Methods of fabricating MEMS with spacers between plates and devices formed by same

ABSTRACT

Methods of fabricating an electromechanical systems (EMS) device with spacers between plates and EMS devices formed by the same are disclosed. In one embodiment, a EMS device is fabricated by laminating a front substrate and a carrier, each of which has components preformed thereon. The front substrate is provided with stationary electrodes formed thereover. A carrier including movable electrodes formed thereover is attached to the front substrate. The carrier may be released after transferring the movable electrodes to the front substrate. In other embodiments, the carrier stays over the front substrate, and serves as a backplate for the EMS device. Features are formed by deposition and patterning, by embossing, or by patterning and etching. Spacers are provided between the front substrate and the backplate to maintain a gap therebetween. The resulting EMS devices can trap smaller volumes between laminated substrates and are less susceptible to pressure variations and moisture leakage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 12/752,982, filed Apr. 1, 2010, which is adivisional of and claims priority to U.S. patent application Ser. No.11/863,079, filed Sep. 27, 2007, now U.S. Pat. No. 7,719,752, whichclaims the priority benefit under 35 U.S.C. §119(e) of ProvisionalApplication Ser. No. 60/917,609, filed May 11, 2007. The fulldisclosures of the foregoing applications are incorporated herein byreference. This application is also related to U.S. Patent ApplicationPublication No. 2006/0067646 A1, entitled MEMS DEVICE FABRICATED ON APRE-PATTERNED SUBSTRATE.

BACKGROUND

1. Field

This invention relates to microelectromechanical devices and methods formaking the same. More particularly, this invention relates tointerferometric modulators and methods for making the same.

2. Description of the Related Art

Microelectromechanical systems (MEMS) include micro mechanical elements,actuators, and electronics. Micromechanical elements may be createdusing deposition, etching, and or other micromachining processes thatetch away parts of substrates and/or deposited material layers or thatadd layers to form electrical and electromechanical devices. One type ofMEMS device is called an interferometric modulator. As used herein, theterm interferometric modulator or interferometric light modulator refersto a device that selectively absorbs and/or reflects light using theprinciples of optical interference. In certain embodiments, aninterferometric modulator may comprise a pair of conductive plates, oneor both of which may be transparent and/or reflective in whole or partand capable of relative motion upon application of an appropriateelectrical signal. In a particular embodiment, one plate may comprise astationary layer deposited on a substrate and the other plate maycomprise a metallic membrane separated from the stationary layer by anair gap. As described herein in more detail, the position of one platein relation to another can change the optical interference of lightincident on the interferometric modulator. Such devices have a widerange of applications, and it would be beneficial in the art to utilizeand/or modify the characteristics of these types of devices so thattheir features can be exploited in improving existing products andcreating new products that have not yet been developed.

SUMMARY

Methods of fabricating a microelectromechanical systems (MEMS) deviceand MEMS devices formed by the same are provided. In one aspect, a MEMSdevice is fabricated by attaching a front substrate and a carrier, eachof which has features preformed thereon. The features can be formed bydeposition and patterning or by shaping (e.g., embossing, patterning andetching, or inscribing). In some embodiments in which features areformed by shaping and deposition, multiple patterns are formed usingmultiple levels without using separate masks. In another aspect, methodsof forming routing structures for MEMS devices are provided. In yetanother aspect, MEMS devices are provided with spacing structures tomaintain a space between a front substrate and a backplate. In anotheraspect, methods for forming black masks to prevent unwanted reflectionsin optical MEMS (e.g., interferometric modulators) are provided. Themethods described above not only reduce the manufacturing costs, butalso provide a higher yield. The resulting MEMS devices are lesssusceptible to pressure variations and moisture leakage.

In one aspect, a method of making a MEMS device is provided. The methodincludes: providing a transparent electrode assembly comprising atransparent substrate and an at least partially transparent electrodeformed over the transparent substrate; providing a carrier comprising areflective electrode formed thereover; and attaching the transparentelectrode assembly to the carrier such that the reflective electrodefaces the at least partially transparent electrode to form a cavity.

In another aspect, a method of making an interferometric device array isprovided. The method includes providing a front substrate comprisingsupports defining cavities on the front substrate. The front substratefurther comprises front electrodes formed in the cavities. The methodfurther includes providing a carrier comprising movable electrodesformed thereover; and attaching the front substrate to the carrier suchthat the movable electrodes face at least a portion of the frontelectrodes to form one or more interferometric devices.

In yet another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes: a front substrate comprising a pluralityof supports defining cavities on the front substrate; and a plurality ofmovable electrodes supported by the supports. Each of the movableelectrodes includes first portions overlying the supports and secondportions neighboring first portions. The second portions do not overliethe supports. The first portions have a first thickness. The secondportions have a second thickness. The second thickness is greater thanthe first thickness.

In yet another aspect, an array of microelectromechanical systems (MEMS)devices is provided. The array includes a front substrate comprising aplurality of supports defining cavities on the front substrate, whereineach of the cavities has a bottom surface. The device further includes abackplate substantially opposing and overlying the front substrate. Thebackplate has a surface facing the cavities of the front substrate. Thesurface is most removed from the front substrate. The device alsoincludes a plurality of mechanical strips interposed between thesupports and the surface of the backplate. Each of the mechanical stripsserves as moving electrodes for multiple MEMS devices. A distancebetween the bottom surface of one of the cavities and the most removedsurface of the backplate is between about 6,500 Å and about 20 μm.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a substrate comprising a plurality ofsupports integrally formed with and of the same material as thesubstrate; and a plurality of mechanical elements defining movingelectrodes. The mechanical elements are supported on top of thesupports.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a substrate having a surface. Thesubstrate includes a plurality of troughs formed into the surface. Thetroughs extend substantially parallel to one another. The surface of thesubstrate defines a higher region of the substrate whereas the troughsdefines lower regions of the substrate. The device further includes aplurality of fixed electrodes formed on the lower regions of thesubstrate.

In yet another aspect, a front substrate for a microelectromechanicalsystem (MEMS) is provided. The front substrate includes a substratecomprising a plurality of supports defining a plurality of cavities onthe substrate. The supports are integrally formed with and of the samematerial as the substrate. The front substrate further includes aconductive layer formed in the cavities between the supports.

In another aspect, a method of making an interferometric modulator isprovided. The method includes forming a plurality of supports from asubstrate. The supports are integrally formed with and of the samematerial as the substrate. The method further includes forming aplurality of mechanical elements defining moving electrodes such thatthe mechanical elements are supported on the supports.

In another aspect, a method of making a microelectromechanical system(MEMS) is provided. The method includes providing a planar substrate;and forming support structures integral with the substrate to defineheights of MEMS cavities. The MEMS cavities have floors, and the MEMScavities are configured to accommodate motion of moving electrodestherein. The method further includes forming a conductive layer on thefloors of the cavities.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate comprising a pluralityof electrodes formed over the front substrate; and a carriersubstantially opposing the front substrate such that the electrodes areinterposed between the carrier and the front substrate. The carrierincludes a plurality of rails extending from the carrier. The devicefurther includes a plurality of movable electrodes interposed betweenthe front substrate and the rails of the carrier.

In another aspect, a carrier for attaching to a microelectromechanicalsystem (MEMS) front substrate with a stationary electrode formedthereover is provided. The carrier includes a substrate including aplurality of rails. The rails define troughs alternating with the rails.The carrier also includes an electrode layer comprising first portionsformed over the rails and second portions formed within the troughs. Theelectrode layer is discontinuous between the troughs and the rails.

In yet another aspect, a method of making a microelectromechanicalsystem (MEMS) array is provided. The MEMS array includes a frontsubstrate having a first surface. The front substrate includes aplurality of fixed lower electrodes formed over the first surface. Themethod includes shaping a carrier substrate so as to have mesasintegrally formed from the carrier substrate. The mesas define troughsalternating with the mesas. The method further includes depositing amechanical layer over the mesas and within the troughs of the carriersubstrate. The mechanical layer is discontinuous between the troughs andthe mesas.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate comprising a firstsupport extending from the front substrate; a backplate having a surfacesubstantially opposing the front substrate such that the first supportis interposed between the front substrate and the surface of thebackplate; and a moving electrode interposed between the front substrateand backplate. The moving electrode includes a portion supported on thefirst support. The device further includes a second support extendingfrom one of the first support of the front substrate and the surface ofthe backplate. The second support is positioned between the firstsupport of the front substrate and the surface of the backplate.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate having a first surface.The front substrate includes an optical stack formed over the firstsurface. The device also includes a backplate opposing the frontsubstrate. The backplate has a second surface facing the first surface.The backplate includes posts extending from the second surface towardthe first surface such that the height of the posts defines a distancebetween the first surface and the second surface. The device furtherincludes a plurality of movable electrode strips extending substantiallyparallel to one another. The strips are interposed between the firstsurface and the second surface.

In yet another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate and a backplate opposingthe front substrate. The backplate has a surface facing the frontsubstrate. The device also includes a plurality of movable electrodestrips extending substantially parallel to one another. The strips areinterposed between the front substrate and the backplate. Portions ofthe strips are movable toward the front substrate. The device furtherincludes a plurality of posts extending from the surface of thebackplate such that the posts are arranged to limit movement of theportions of the strips toward the surface.

In another aspect, a method of making microelectromechanical system(MEMS) device is provided. The method includes providing a frontsubstrate comprising a first support extending from the front substrate;providing a backplate having a surface; attaching the front substrate tothe backplate such that the first support is interposed between thefront substrate and the surface of the backplate; and forming a secondsupport between the first support of the front substrate and the surfaceof the backplate such that the second support extends from one of thefirst support of the front substrate and the surface of the backplate.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate having a first surface.The front substrate includes an array region and a peripheral region onthe first surface. The device also includes a backplate having a secondsurface facing the first surface. The first and second surfaces have agap therebetween. The backplate includes an array region and aperipheral region on the second surface. The device further includes aconductive line extending on the peripheral region of the frontsubstrate; and a conductive structure extending between the peripheralregions of the front substrate and the backplate. The conductivestructure contacts the conductive line.

In another aspect, a carrier assembly for making an interferometricmodulator is provided. The interferometric modulator includes a frontsubstrate comprising substantially transparent electrodes formedthereon. The carrier assembly includes a releasable structure having asurface; and a plurality of elongated conductive strips formed over thesurface. The elongated conductive strips extend in a directionsubstantially parallel to one another.

In another aspect, an interferometric modulator is provided. Theinterferometric modulator includes a carrier assembly which includes areleasable structure having a surface, and a plurality of elongatedconductive strips formed over the surface. The elongated conductivestrips extend in a direction substantially parallel to one another. Theinterferometric modulator also includes a front substrate comprising aplurality of supports and substantially transparent electrodes. Thefront substrate is attached to the carrier assembly such that theconductive strips are supported by the supports.

In yet another aspect, a method of making an interferometric modulatoris provided. The interferometric modulator includes a front substratecomprising a plurality of supports defining cavities on the frontsubstrate. The front substrate further includes lower electrodes formedin the cavities. The method includes providing a releasable structurehaving a surface; depositing a movable electrode material over thesurface; providing a mask over the movable electrode material so as toselectively expose portions of the movable electrode material; andselectively etching the movable electrode material using the mask,thereby forming a plurality of movable electrode strips. The movableelectrode strips extend in a direction substantially parallel to oneanother. The method further includes positioning the releasablestructure over the front substrate such that the movable electrodestrips face the cavities of the front substrate.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate comprising an arrayregion and a peripheral region. The front substrate comprises aplurality of supports defining a plurality of lower regions therebetweenin the array region. The front substrate further comprises a land in theperipheral region. At least a portion of the land has substantially thesame height as the supports in the array region. The device alsoincludes a plurality of conductors formed over the land in theperipheral region. The conductors are electrically isolated from oneanother. The device further includes a conductive layer formed on thelower regions of the front substrate.

In another aspect, a carrier for combining with a front substrate of aninterferometric modulator is provided. The front substrate includessubstantially transparent electrodes formed thereon. The carrierincludes a substrate including an array region and a peripheral region;and a plurality of movable electrode strips formed over the array regionof the substrate. The strips extend substantially parallel to oneanother. The carrier further includes a plurality of routing tracesformed over the substrate. Each of the traces extends from a respectiveone of the strips to the peripheral region.

In yet another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate including an arrayregion and a peripheral region. The front substrate includes a pluralityof rails extending parallel to one another in the array region. Therails define a plurality of troughs in the array region. The frontsubstrate further includes trenches in the peripheral region. Each ofthe trenches extends from a respective one of the troughs. The devicefurther includes row routing traces formed in the trenches. The rowrouting traces extend from the troughs in the array region to the atleast one portion of the peripheral region. The row routing traces areelectrically isolated from one another.

In another aspect, a microelectromechanical system (MEMS) device isprovided. The device includes a front substrate having a surfacecomprising an array region and a peripheral region surrounding the arrayregion. The front substrate includes an annular sealing region on thesurface of the front substrate. The sealing region substantiallysurrounds the array region. The sealing region has a first widthextending in a direction toward the array region. The front substratealso includes a recess formed into the substrate. The recess has asecond width extending in the direction. The second width is greaterthan the first width. The recess extends across a portion of the sealingregion. The recess defines an elevation lower than that of the surfaceof the front substrate. The front substrate further includes a firstconductive layer formed on the surface of the front substrate; and asecond conductive layer formed in the recess, wherein the first andsecond conductive layers are discontinuous with each other.

In another aspect, a method of making a microelectromechanical system(MEMS) device is provided. The method includes providing a frontsubstrate having a surface comprising an array region and a routingregion; and forming an isolation trench in the routing region of thesurface of the front substrate. The isolation trench includes a bottomsurface and sidewalls. The bottom surface of the isolation trenchdefines an elevation lower than that of the surface of the frontsubstrate. The method further includes forming a conductive layer on thesurface of the substrate and the bottom surface of the isolation trenchsuch that the conductive layer is discontinuous between the surface ofthe substrate and the isolation trench.

In another aspect, a method of making an interferometric modulator isprovided. The method includes providing a substrate comprising cavitieson a surface thereof; providing a liquid mixture comprising alight-absorbing material over the surface of the substrate such that theliquid mixture fills at least portions of the cavities; and partiallyremoving a component of the liquid mixture from the cavities of thesubstrate after providing the liquid mixture such that at least aportion of the light-absorbing material remains in the cavities.

In another aspect, an interferometric modulator is provided. Theinterferometric modulator includes a substrate having a surface. Thesubstrate includes a plurality of supports formed on the surface of thesubstrate. The interferometric modulator also includes a light-absorbingmaterial formed on the surface of the substrate. Substantially all ofthe material is positioned in corners where the supports meet thesurface.

In yet another aspect, a method of making an interferometric modulatoris provided. The method includes forming support structures over asubstrate; and depositing a black mask material over the substrate afterforming the support structures.

In another aspect, a method of making a static interferometric displaydevice is provided. The method includes providing a first substratecomprising a partially transparent layer formed thereon. The firstsubstrate is formed of a substantially transparent material. The methodalso includes providing a second substrate comprising a mirror layerformed thereon. At least one of the first and second substrates includescavities patterned based on an image which the static interferometricdevice is configured to display. The method further includes laminatingthe first substrate with the second substrate. The partially transparentlayer faces the second substrate. The mirror layer faces the firstsubstrate. The cavities of one of the substrates face the other of thesubstrates.

In another aspect, a method of making a static interferometric displaydevice is provided. The method includes providing a first substratecomprising a first surface including a plurality of cavities. Thecavities have at least one depth. The cavities are patterned at leastpartially based on an image which the static interferometric displaydevice is configured to display. The method also includes providing asecond substrate including a second surface; and attaching the firstsubstrate to the second substrate such that the first surface faces thesecond surface.

In yet another aspect, a static interferometric display device isprovided. The device includes a first substrate including a firstsurface. The first substrate includes cavities defined on the firstsurface. The cavities are patterned at least partially based on an imagewhich the static interferometric display device is configured todisplay. The first substrate is formed of a substantially transparentmaterial. The device also includes a second substrate attached to thefirst substrate. The second substrate includes a second surface facingthe first surface. The device further includes a partially reflectivelayer in the cavities of the first substrate.

In yet another aspect, a static interferometric display device isprovided. The device includes a first substrate including a firstsurface. The first substrate includes cavities defined on the firstsurface. The cavities are patterned at least partially based on an imagewhich the static interferometric display device is configured todisplay. The device also includes a second substrate attached to thefirst substrate. The second substrate includes a second surface facingthe first surface. The second substrate is formed of a substantiallytransparent material. The device further includes a mirror layer on thefirst surface of the first substrate; and a partially reflective layeron the second surface of the second substrate.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described above and as further described below. Of course, it is tobe understood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

All of these embodiments will also be better understood with referenceto the appended claims and drawings which form part of this disclosure.In addition, various changes, modifications, combinations andsub-combinations may be made without departing from the spirit and scopeof the invention, as defined by the appended claims. These and otherembodiments of the invention will become readily apparent to thoseskilled in the art from the following detailed description of thepreferred embodiments having reference to the attached figures, theinvention not being limited to any particular preferred embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view depicting a portion of one embodiment of aninterferometric modulator display in which a movable reflective layer ofa first interferometric modulator is in a relaxed position and a movablereflective layer of a second interferometric modulator is in an actuatedposition.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device incorporating a 3×3 interferometric modulator display.

FIG. 3 is a diagram of movable mirror position versus applied voltagefor one exemplary embodiment of an interferometric modulator of FIG. 1.

FIG. 4 is an illustration of a set of row and column voltages that maybe used to drive an interferometric modulator display.

FIGS. 5A and 5B illustrate one exemplary timing diagram for row andcolumn signals that may be used to write a frame of display data to the3×3 interferometric modulator display of FIG. 2.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa visual display device comprising a plurality of interferometricmodulators.

FIG. 7A is a cross section of the device of FIG. 1.

FIG. 7B is a cross section of an alternative embodiment of aninterferometric modulator.

FIG. 7C is a cross section of another alternative embodiment of aninterferometric modulator.

FIG. 7D is a cross section of yet another alternative embodiment of aninterferometric modulator.

FIG. 7E is a cross section of an additional alternative embodiment of aninterferometric modulator.

FIG. 8 is a top plan view of one embodiment of an interferometricmodulator display device.

FIG. 9 is an exploded perspective view of one embodiment of aninterferometric modulator display device.

FIG. 10 is a partial perspective view of one embodiment of a shapedfront substrate of an interferometric modulator display device.

FIG. 11A is a cross section of the shaped front substrate of FIG. 10without an optical stack.

FIG. 11B is a cross section of the shaped front substrate of FIG. 11Aafter deposition of an optical stack.

FIGS. 12A-12D illustrates one embodiment of a method of forming a shapedfront substrate like that of FIGS. 10-11B.

FIG. 13 illustrates a partial perspective view of an array or displayregion of a partially fabricated interferometric modulator displaydevice according to one embodiment.

FIG. 14A is a top plan view of the partially fabricated interferometricmodulator display device of FIG. 13.

FIG. 14B is a cross section of the partially fabricated interferometricmodulator display device of FIG. 13, taken along lines 14B-14B.

FIG. 14C is a cross section of the partially fabricated interferometricmodulator display device of FIG. 13, taken along lines 14C-14C, with aback wall formed by continuous rails omitted for clarity.

FIG. 14D is an enlarged cross section of the partially fabricatedinterferometric modulator display device of FIG. 14B.

FIG. 15 is a top plan view of a partially fabricated interferometricmodulator display device according to one embodiment, schematicallyillustrating interconnects for row and column drivers.

FIG. 16A is a top plan view of a shaped front substrate having columnand row routing structures according to one embodiment.

FIG. 16B is an enlarged top plan view of one of the row routingstructures of FIG. 16A.

FIG. 16C is a cross section of the row routing structure of FIG. 16B,taken along lines 16C-16C, according to one embodiment.

FIG. 16D is a cross section of the row routing structure of FIG. 16B,taken along lines 16C-16C, according to another embodiment.

FIG. 16E is a cross section of the row routing structure of FIG. 16B anda row driver with an anisotropic conductive film interposed therebetweenaccording to one embodiment.

FIG. 16F is a cross section of the row routing structure of FIG. 16E,taken along lines 16F-16F.

FIG. 17A is a partial perspective view of one embodiment of a routingstructure for movable electrodes.

FIG. 17B is a cross section of the routing structure of FIG. 17A, takenalong lines 17B-17B.

FIG. 17C is a cross section of the routing structure of FIG. 17A, takenalong lines 17C-17C.

FIG. 18A is a partial perspective view of another embodiment of arouting structure for movable electrodes.

FIG. 18B is a cross section of the routing structure of FIG. 18A, takenalong lines 18B-18B.

FIG. 18C is a cross section of the routing structure of FIG. 18A, takenalong lines 18C-18C.

FIG. 19 is a top plan view of one embodiment of a carrier having routingtraces for movable electrodes for joining with a front substrate havingstationary electrodes.

FIG. 20 is a schematic perspective view illustrating one embodiment of amethod of forming an optical stack on a shaped front substrate using ashadow mask.

FIG. 21 is a schematic perspective view illustrating a method of formingthe routing structure of FIG. 17A using a shadow mask according to oneembodiment.

FIGS. 22A-22C illustrate one embodiment of a method of making a frontsubstrate using conventional depositing and patterning techniques.

FIGS. 23A-23C illustrate one embodiment of a method of making a frontsubstrate having deposited preformed supports that are patterned priorto depositing lower electrode and dielectric layers.

FIGS. 24A and 24B are cross sections of routing structures for movableelectrodes on a carrier for joining with a front substrate havingstationary electrodes, according to one embodiment.

FIG. 25 is a perspective view of a shaped carrier for joining with afront substrate having stationary electrodes, according to oneembodiment.

FIGS. 26A-26E are schematic cross sections illustrating one embodimentof a method of making a shaped carrier for joining with a frontsubstrate having stationary electrodes.

FIG. 27A is a partial perspective view of a shaped carrier backplatehaving edge rails and posts according to one embodiment.

FIG. 27B is a cross-section of the shaped carrier backplate of FIG. 27A,taken along lines 27B-27B.

FIG. 27C is a cross-section of the shaped carrier backplate of FIG. 27A,taken along lines 27C-27C.

FIG. 27D is a top plan view of the shaped carrier backplate of FIG. 27A.

FIG. 28 is a partial perspective view of a shaped carrier backplatehaving movable electrodes with etch holes according to anotherembodiment.

FIGS. 29A-29D are a series of schematic cross-sections illustrating oneembodiment of a method of making a shaped carrier backplate.

FIGS. 30A-30D illustrate another embodiment of a method of making ashaped carrier backplate.

FIGS. 31A-31D illustrate yet another embodiment of a method of making ashaped carrier backplate.

FIGS. 32A-32C are schematic cross sections of embodiments of shapedcarrier backplates.

FIG. 32D is a schematic top plan view of the shaped carrier backplate ofFIG. 32B.

FIG. 32E is a schematic cross section of an edge portion of the shapedcarrier backplate of FIG. 32D.

FIGS. 33A-33D illustrate yet another embodiment of a method of making ashaped carrier backplate having patterned movable electrodes.

FIG. 34A is a schematic partial perspective view of an interferometricmodulator display device having excess mechanical layer supportselevated between movable electrode strips according to one embodiment.

FIGS. 34B-34D are schematic cross sections of the interferometricmodulator display device of FIG. 34A, taken along lines 34B-34B,34C-34C, and 34D-34D, respectively.

FIGS. 35A and 35B are schematic, perspective views illustrating oneembodiment of a method of making a removable carrier for transferring amovable electrode to a front substrate.

FIGS. 35C and 35D are schematic cross sections illustrating oneembodiment of a method of making an interferometric modulator displaydevice using a removable carrier.

FIGS. 36A-36E are schematic cross sections illustrating one embodimentof a method of making a carrier with patterned movable electrodes.

FIGS. 37A-37E illustrate another embodiment of a method of making acarrier with patterned movable electrodes.

FIGS. 38A-38D illustrate yet another embodiment of a method of making acarrier with patterned movable electrodes.

FIG. 39A is a schematic cross section of a carrier for joining with afront substrate, the carrier having a rivet support structure accordingto one embodiment.

FIG. 39B is a schematic cross section of an interferometric modulatordisplay device having the rivet support structure of FIG. 39A invertedover a front substrate support structure according to one embodiment.

FIG. 40 is a schematic, perspective view of one embodiment of aninterferometric modulator display device.

FIGS. 41A-41C schematically illustrate routing arrangements ofinterferometric modulator display devices according to variousembodiments.

FIG. 42A illustrates a routing arrangement of an interferometricmodulator display device according to another embodiment.

FIGS. 42B and 42C are cross sections of the interferometric modulatordisplay device of FIG. 42A, taken along the lines 42A-42A and 42B-42B,respectively.

FIG. 43A is a schematic perspective view and FIGS. 43B-43C are schematiccross sections illustrating one embodiment of a method of making aninterferometric modulator display device using a carrier that alsoserves as a backplate for the completed device.

FIG. 44A is a schematic plan view, FIG. 44B is an enlarged view, andFIGS. 44C-44E are schematic cross sections illustrating one embodimentof a method of using a shadow mask with conductive sealant on a frontsubstrate.

FIGS. 45A-45D are schematic cross sections illustrating one embodimentof a method of making an interferometric modulator display device usinga removable carrier.

FIG. 46A is a cross section of one embodiment of an interferometricmodulator display device having spacers extending between a movableelectrode layer and a backplate.

FIG. 46B is a perspective view of the interferometric modulator displaydevice of FIG. 46A having spacers and supports trapping a movableelectrode layer.

FIG. 47 is a perspective view of yet another embodiment of aninterferometric modulator display device having spacers extendingthrough the movable electrode layer.

FIG. 48 is a perspective view of yet another embodiment of aninterferometric modulator display device having spacers.

FIG. 49A is a cross section of one embodiment of an interferometricmodulator display device having stop posts extending from a backplate.

FIG. 49B is a cross section of another embodiment of an interferometricmodulator display device having stop posts extending from a backplate.

FIG. 49C is a cross section of yet another embodiment of aninterferometric modulator display device having stop posts extendingfrom a backplate.

FIG. 50 is a cross section of one embodiment of an interferometricmodulator display device having no support in the display regionthereof.

FIG. 51 is a cross section of one embodiment of an interferometricmodulator display device having spacers extending from a backplate to afront substrate.

FIG. 52A is a cross section of one embodiment of an interferometricmodulator display device having a patterned black mask.

FIG. 52B is a top plan view of the interferometric modulator displaydevice of FIG. 50A according to one embodiment.

FIGS. 53A-53C illustrate one embodiment of a method of making a partialwetting black mask for an interferometric modulator display device.

FIG. 53D illustrates another embodiment of an interferometric modulatordisplay device having a partial wetting black mask.

FIG. 54 is a cross section of one embodiment of a static interferometricdisplay including a shaped front substrate.

FIG. 55 is a cross section of another embodiment of a staticinterferometric display including a shaped backplate.

FIG. 56 is a top plan view of the static interferometric display of FIG.54.

FIG. 57 is a cross section of another embodiment of a staticinterferometric display including a shaped front substrate.

FIG. 58 is a cross section of yet another embodiment of a staticinterferometric display including a shaped front substrate withoutseparate supports for each pixel.

FIG. 59 is a top plan view of the static interferometric display of FIG.58.

FIG. 60 is a cross section of another embodiment of a staticinterferometric display including a shaped backplate.

FIG. 61 is a cross section of another embodiment of a staticinterferometric display including a shaped front substrate.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description is directed to certain specificembodiments of the invention. However, the invention can be embodied ina multitude of different ways. In this description, reference is made tothe drawings wherein like parts are designated with like numeralsthroughout. As will be apparent from the following description, theembodiments may be implemented in any device that is configured todisplay an image, whether in motion (e.g., video) or stationary (e.g.,still image), and whether textual or pictorial. More particularly, it iscontemplated that the embodiments may be implemented in or associatedwith a variety of electronic devices such as, but not limited to, mobiletelephones, wireless devices, personal data assistants (PDAs), hand-heldor portable computers, GPS receivers/navigators, cameras, MP3 players,camcorders, game consoles, wrist watches, clocks, calculators,television monitors, flat panel displays, computer monitors, autodisplays (e.g., odometer display, etc.), cockpit controls and/ordisplays, display of camera views (e.g., display of a rear view camerain a vehicle), electronic photographs, electronic billboards or signs,projectors, architectural structures, packaging, and aestheticstructures (e.g., display of images on a piece of jewelry). MEMS devicesof similar structure to those described herein can also be used innon-display applications such as in electronic switching devices.

A microelectromechanical systems (MEMS) device may be fabricated byattaching two substrates, each of which has components preformedthereon. A method of making a MEMS device according to one embodimentincludes providing a front substrate and stationary electrodes formedover the front substrate. Then, a carrier including movable electrodesformed thereover is attached to the front substrate. The carrier of someembodiments can be released after transferring the movable electrodes tothe front substrates; in other embodiments, the carrier serves as abackplate for the MEMS. Features can be formed by deposition andpatterning, by embossing, or by patterning and etching. The method notonly reduces the manufacturing costs, but also provides less variationand therefore higher yield. The resulting MEMS device is lesssusceptible to pressure variations and moisture leakage. Also disclosedare methods of routing from movable electrodes to column drivers andfrom stationary electrodes to row drivers. Techniques for forming blackmasks to prevent unwanted reflections in optical MEMS (e.g.,interferometric modulators) are also taught.

One interferometric modulator display embodiment comprising aninterferometric MEMS display element is illustrated in FIG. 1. In thesedevices, the pixels are in either a bright or dark state. In the bright(“on” or “open”) state, the display element reflects a large portion ofincident visible light to a user. When in the dark (“off” or “closed”)state, the display element reflects little incident visible light to theuser. Depending on the embodiment, the light reflectance properties ofthe “on” and “off” states may be reversed. MEMS pixels can be configuredto reflect predominantly at selected colors, allowing for a colordisplay in addition to black and white.

FIG. 1 is an isometric view depicting two adjacent pixels in a series ofpixels of a visual display, wherein each pixel comprises a MEMSinterferometric modulator. In some embodiments, an interferometricmodulator display comprises a row/column array of these interferometricmodulators. Each interferometric modulator includes a pair of reflectivelayers positioned at a variable and controllable distance from eachother to form a resonant optical cavity with at least one variabledimension. In one embodiment, one of the reflective layers may be movedbetween two positions. In the first position, referred to herein as therelaxed position, the movable reflective layer is positioned at arelatively large distance from a fixed partially reflective layer. Inthe second position, referred to herein as the actuated position, themovable reflective layer is positioned more closely adjacent to thepartially reflective layer. Incident light that reflects from the twolayers interferes constructively or destructively depending on theposition of the movable reflective layer, producing either an overallreflective or non-reflective state for each pixel.

The depicted portion of the pixel array in FIG. 1 includes two adjacentinterferometric modulators 12 a and 12 b. In the interferometricmodulator 12 a on the left, a movable reflective layer 14 a isillustrated in a relaxed position at a predetermined distance from anoptical stack 16 a, which includes a partially reflective layer. In theinterferometric modulator 12 b on the right, the movable reflectivelayer 14 b is illustrated in an actuated position adjacent to theoptical stack 16 b.

The optical stacks 16 a and 16 b (collectively referred to as opticalstack 16), as referenced herein, typically comprise of several fusedlayers, which can include an electrode layer, such as indium tin oxide(ITO), a partially reflective layer, such as chromium, and a transparentdielectric. The optical stack 16 is thus electrically conductive,partially transparent and partially reflective, and may be fabricated,for example, by depositing one or more of the above layers onto atransparent substrate 20. In some embodiments, the layers are patternedinto parallel strips, and may form row electrodes in a display device asdescribed further below. The movable reflective layers 14 a, 14 b may beformed as a series of parallel strips of a deposited metallic layer orlayers (orthogonal to the row electrodes of 16 a, 16 b) deposited on topof posts 18 and an intervening sacrificial material deposited betweenthe posts 18. When the sacrificial material is etched away, the movablereflective layers 14 a, 14 b are separated from the optical stacks 16 a,16 b by a defined gap or cavity 19. A highly conductive and reflectivematerial such as aluminum may be used for the reflective layers 14, andthese strips may form column electrodes in a display device.

With no applied voltage, the cavity 19 remains between the movablereflective layer 14 a and optical stack 16 a, with the movablereflective layer 14 a in a mechanically relaxed state, as illustrated bythe pixel 12 a in FIG. 1. However, when a potential difference isapplied to a selected row and column, the capacitor formed at theintersection of the row and column electrodes at the corresponding pixelbecomes charged, and electrostatic forces pull the electrodes together.If the voltage is high enough, the movable reflective layer 14 isdeformed and is forced against the optical stack 16. A dielectric layer(not illustrated in this Figure) within the optical stack 16 may preventshorting and control the separation distance between layers 14 and 16,as illustrated by pixel 12 b on the right in FIG. 1. The behavior is thesame regardless of the polarity of the applied potential difference. Inthis way, row/column actuation that can control the reflective vs.non-reflective pixel states is analogous in many ways to that used inconventional LCD and other display technologies.

FIGS. 2 through 5 illustrate one exemplary process and system for usingan array of interferometric modulators in a display application.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device that may incorporate aspects of the invention. In theexemplary embodiment, the electronic device includes a processor 21which may be any general purpose single- or multi-chip microprocessorsuch as an ARM, Pentium®, Pentium II®, Pentium III®, Pentium IV®,Pentium® Pro, an 8051, a MIPS®, a Power PC®, an ALPHA®, or any specialpurpose microprocessor such as a digital signal processor,microcontroller, or a programmable gate array. As is conventional in theart, the processor 21 may be configured to execute one or more softwaremodules. In addition to executing an operating system, the processor maybe configured to execute one or more software applications, including aweb browser, a telephone application, an email program, or any othersoftware application.

In one embodiment, the processor 21 is also configured to communicatewith an array driver 22. In one embodiment, the array driver 22 includesa row driver circuit 24 and a column driver circuit 26 that providesignals to a panel or display array (display) 30. The cross section ofthe array illustrated in FIG. 1 is shown by the lines 1-1 in FIG. 2. ForMEMS interferometric modulators, the row/column actuation protocol maytake advantage of a hysteresis property of these devices illustrated inFIG. 3. It may require, for example, a 10 volt potential difference tocause a movable layer to deform from the relaxed state to the actuatedstate. However, when the voltage is reduced from that value, the movablelayer maintains its state as the voltage drops back below 10 volts. Inthe exemplary embodiment of FIG. 3, the movable layer does not relaxcompletely until the voltage drops below 2 volts. There is thus a rangeof voltage, about 3 to 7 V in the example illustrated in FIG. 3, wherethere exists a window of applied voltage within which the device isstable in either the relaxed or actuated state. This is referred toherein as the “hysteresis window” or “stability window.” For a displayarray having the hysteresis characteristics of FIG. 3, the row/columnactuation protocol can be designed such that during row strobing, pixelsin the strobed row that are to be actuated are exposed to a voltagedifference of about 10 volts, and pixels that are to be relaxed areexposed to a voltage difference of close to zero volts. After thestrobe, the pixels are exposed to a steady state voltage difference ofabout 5 volts such that they remain in whatever state the row strobe putthem in. After being written, each pixel sees a potential differencewithin the “stability window” of 3-7 volts in this example. This featuremakes the pixel design illustrated in FIG. 1 stable under the sameapplied voltage conditions in either an actuated or relaxed pre-existingstate. Since each pixel of the interferometric modulator, whether in theactuated or relaxed state, is essentially a capacitor formed by thefixed and moving reflective layers, this stable state can be held at avoltage within the hysteresis window with almost no power dissipation.Essentially no current flows into the pixel if the applied potential isfixed.

In typical applications, a display frame may be created by asserting theset of column electrodes in accordance with the desired set of actuatedpixels in the first row. A row pulse is then applied to the row 1electrode, actuating the pixels corresponding to the asserted columnlines. The asserted set of column electrodes is then changed tocorrespond to the desired set of actuated pixels in the second row. Apulse is then applied to the row 2 electrode, actuating the appropriatepixels in row 2 in accordance with the asserted column electrodes. Therow 1 pixels are unaffected by the row 2 pulse, and remain in the statethey were set to during the row 1 pulse. This may be repeated for theentire series of rows in a sequential fashion to produce the frame.Generally, the frames are refreshed and/or updated with new display databy continually repeating this process at some desired number of framesper second. A wide variety of protocols for driving row and columnelectrodes of pixel arrays to produce display frames are also well knownand may be used in conjunction with the present invention.

FIGS. 4 and 5 illustrate one possible actuation protocol for creating adisplay frame on the 3×3 array of FIG. 2. FIG. 4 illustrates a possibleset of column and row voltage levels that may be used for pixelsexhibiting the hysteresis curves of FIG. 3. In the FIG. 4 embodiment,actuating a pixel involves setting the appropriate column to −V_(bias),and the appropriate row to +ΔV, which may correspond to −5 volts and +5volts respectively Relaxing the pixel is accomplished by setting theappropriate column to +V_(bias), and the appropriate row to the same+ΔV, producing a zero volt potential difference across the pixel. Inthose rows where the row voltage is held at zero volts, the pixels arestable in whatever state they were originally in, regardless of whetherthe column is at +V_(bias), or −V_(bias). As is also illustrated in FIG.4, it will be appreciated that voltages of opposite polarity than thosedescribed above can be used, e.g., actuating a pixel can involve settingthe appropriate column to +V_(bias), and the appropriate row to −ΔV. Inthis embodiment, releasing the pixel is accomplished by setting theappropriate column to −V_(bias), and the appropriate row to the same−ΔV, producing a zero volt potential difference across the pixel.

FIG. 5B is a timing diagram showing a series of row and column signalsapplied to the 3×3 array of FIG. 2 which will result in the displayarrangement illustrated in FIG. 5A, where actuated pixels arenon-reflective. Prior to writing the frame illustrated in FIG. 5A, thepixels can be in any state, and in this example, all the rows are at 0volts, and all the columns are at +5 volts. With these applied voltages,all pixels are stable in their existing actuated or relaxed states.

In the FIG. 5A frame, pixels (1,1), (1,2), (2,2), (3,2) and (3,3) areactuated. To accomplish this, during a “line time” for row 1, columns 1and 2 are set to −5 volts, and column 3 is set to +5 volts. This doesnot change the state of any pixels, because all the pixels remain in the3-7 volt stability window. Row 1 is then strobed with a pulse that goesfrom 0, up to 5 volts, and back to zero. This actuates the (1,1) and(1,2) pixels and relaxes the (1,3) pixel. No other pixels in the arrayare affected. To set row 2 as desired, column 2 is set to −5 volts, andcolumns 1 and 3 are set to +5 volts. The same strobe applied to row 2will then actuate pixel (2,2) and relax pixels (2,1) and (2,3). Again,no other pixels of the array are affected. Row 3 is similarly set bysetting columns 2 and 3 to −5 volts, and column 1 to +5 volts. The row 3strobe sets the row 3 pixels as shown in FIG. 5A. After writing theframe, the row potentials are zero, and the column potentials can remainat either +5 or −5 volts, and the display is then stable in thearrangement of FIG. 5A. It will be appreciated that the same procedurecan be employed for arrays of dozens or hundreds of rows and columns. Itwill also be appreciated that the timing, sequence, and levels ofvoltages used to perform row and column actuation can be varied widelywithin the general principles outlined above, and the above example isexemplary only, and any actuation voltage method can be used with thesystems and methods described herein.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa display device 40. The display device 40 can be, for example, acellular or mobile telephone. However, the same components of displaydevice 40 or slight variations thereof are also illustrative of varioustypes of display devices such as televisions and portable media players.

The display device 40 includes a housing 41, a display 30, an antenna43, a speaker 45, an input device 48, and a microphone 46. The housing41 is generally formed from any of a variety of manufacturing processesas are well known to those of skill in the art, including injectionmolding, and vacuum forming. In addition, the housing 41 may be madefrom any of a variety of materials, including but not limited toplastic, metal, glass, rubber, and ceramic, or a combination thereof. Inone embodiment the housing 41 includes removable portions (not shown)that may be interchanged with other removable portions of differentcolor, or containing different logos, pictures, or symbols.

The display 30 of exemplary display device 40 may be any of a variety ofdisplays, including a bi-stable display, as described herein. In otherembodiments, the display 30 includes a flat-panel display, such asplasma, EL, OLED, STN LCD, or TFT LCD as described above, or anon-flat-panel display, such as a CRT or other tube device, as is wellknown to those of skill in the art. However, for purposes of describingthe present embodiment, the display 30 includes an interferometricmodulator display, as described herein.

The components of one embodiment of exemplary display device 40 areschematically illustrated in FIG. 6B. The illustrated exemplary displaydevice 40 includes a housing 41 and can include additional components atleast partially enclosed therein. For example, in one embodiment, theexemplary display device 40 includes a network interface 27 thatincludes an antenna 43 which is coupled to a transceiver 47. Thetransceiver 47 is connected to the processor 21, which is connected toconditioning hardware 52. The conditioning hardware 52 may be configuredto condition a signal (e.g. filter a signal). The conditioning hardware52 is connected to a speaker 45 and a microphone 46. The processor 21 isalso connected to an input device 48 and a driver controller 29. Thedriver controller 29 is coupled to a frame buffer 28 and to the arraydriver 22, which in turn is coupled to a display array 30. A powersupply 50 provides power to all components as required by the particularexemplary display device 40 design.

The network interface 27 includes the antenna 43 and the transceiver 47so that the exemplary display device 40 can communicate with one or moredevices over a network. In one embodiment the network interface 27 mayalso have some processing capabilities to relieve requirements of theprocessor 21. The antenna 43 is any antenna known to those of skill inthe art for transmitting and receiving signals. In one embodiment, theantenna transmits and receives RF signals according to the IEEE 802.11standard, including IEEE 802.11(a), (b), or (g). In another embodiment,the antenna transmits and receives RF signals according to the BLUETOOTHstandard. In the case of a cellular telephone, the antenna is designedto receive CDMA, GSM, AMPS or other known signals that are used tocommunicate within a wireless cell phone network. The transceiver 47pre-processes the signals received from the antenna 43 so that they maybe received by and further manipulated by the processor 21. Thetransceiver 47 also processes signals received from the processor 21 sothat they may be transmitted from the exemplary display device 40 viathe antenna 43.

In an alternative embodiment, the transceiver 47 can be replaced by areceiver. In yet another alternative embodiment, network interface 27can be replaced by an image source, which can store or generate imagedata to be sent to the processor 21. For example, the image source canbe a digital video disc (DVD) or a hard-disc drive that contains imagedata, or a software module that generates image data.

The processor 21 generally controls the overall operation of theexemplary display device 40. The processor 21 receives data, such ascompressed image data from the network interface 27 or an image source,and processes the data into raw image data or into a format that isreadily processed into raw image data. The processor 21 then sends theprocessed data to the driver controller 29 or to the frame buffer 28 forstorage. Raw data typically refers to the information that identifiesthe image characteristics at each location within an image. For example,such image characteristics can include color, saturation, and gray-scalelevel.

In one embodiment, the processor 21 includes a microcontroller, CPU, orlogic unit to control operation of the exemplary display device 40. Theconditioning hardware 52 generally includes amplifiers and filters fortransmitting signals to the speaker 45, and for receiving signals fromthe microphone 46. The conditioning hardware 52 may be discretecomponents within the exemplary display device 40, or may beincorporated within the processor 21 or other components.

The driver controller 29 takes the raw image data generated by theprocessor 21 either directly from the processor 21 or from the framebuffer 28 and reformats the raw image data appropriately for high speedtransmission to the array driver 22. Specifically, the driver controller29 reformats the raw image data into a data flow having a raster-likeformat, such that it has a time order suitable for scanning across thedisplay array 30. Then the driver controller 29 sends the formattedinformation to the array driver 22. Although a driver controller 29,such as a LCD controller, is often associated with the system processor21 as a stand-alone Integrated Circuit (IC), such controllers may beimplemented in many ways. They may be embedded in the processor 21 ashardware, embedded in the processor 21 as software, or fully integratedin hardware with the array driver 22.

Typically, the array driver 22 receives the formatted information fromthe driver controller 29 and reformats the video data into a parallelset of waveforms that are applied many times per second to the hundredsand sometimes thousands of leads coming from the display's x-y matrix ofpixels.

In one embodiment, the driver controller 29, array driver 22, anddisplay array 30 are appropriate for any of the types of displaysdescribed herein. For example, in one embodiment, the driver controller29 is a conventional display controller or a bi-stable displaycontroller (e.g., an interferometric modulator controller). In anotherembodiment, the array driver 22 is a conventional driver or a bi-stabledisplay driver (e.g., an interferometric modulator display). In oneembodiment, the driver controller 29 is integrated with the array driver22. Such an embodiment is common in highly integrated systems such ascellular phones, watches, and other small area displays. In yet anotherembodiment, the display array 30 is a typical display array or abi-stable display array (e.g., a display including an array ofinterferometric modulators).

The input device 48 allows a user to control the operation of theexemplary display device 40. In one embodiment, the input device 48includes a keypad, such as a QWERTY keyboard or a telephone keypad, abutton, a switch, a touch-sensitive screen, a pressure- orheat-sensitive membrane. In one embodiment, the microphone 46 is aninput device for the exemplary display device 40. When the microphone 46is used to input data to the device, voice commands may be provided by auser for controlling operations of the exemplary display device 40.

The power supply 50 can include a variety of energy storage devices asare well known in the art. For example, in one embodiment, the powersupply 50 is a rechargeable battery, such as a nickel-cadmium battery ora lithium ion battery. In another embodiment, the power supply 50 is arenewable energy source, a capacitor, or a solar cell, including aplastic solar cell, and solar-cell paint. In another embodiment, thepower supply 50 is configured to receive power from a wall outlet.

In some implementations control programmability resides, as describedabove, in a driver controller which can be located in several places inthe electronic display system. In some cases control programmabilityresides in the array driver 22. Those of skill in the art will recognizethat the above-described optimization may be implemented in any numberof hardware and/or software components and in various configurations.

The details of the structure of interferometric modulators that operatein accordance with the principles set forth above may vary widely. Forexample, FIGS. 7A-7E illustrate five different embodiments of themovable reflective layer 14 and its supporting structures. FIG. 7A is across section of the embodiment of FIG. 1, where a strip of metalmaterial 14 is deposited on orthogonally extending supports 18. In FIG.7B, the moveable reflective layer 14 is attached to supports at thecorners only, on tethers 32. In FIG. 7C, the moveable reflective layer14 is suspended from a deformable layer 34, which may comprise aflexible metal. The deformable layer 34 connects, directly orindirectly, to the substrate 20 at various locations. The connectionsare herein referred to as support structures or posts 18. The embodimentillustrated in FIG. 7D has support structures 18 including support postplugs 42 upon which the deformable layer 34 rests. The movablereflective layer 14 remains suspended over the cavity, as in FIGS.7A-7C, but the deformable layer 34 does not form the support posts 18 byfilling holes between the deformable layer 34 and the optical stack 16.Rather, the support posts 18 are formed of a planarization material,which is used to form support post plugs 42. The embodiment illustratedin FIG. 7E is based on the embodiment shown in FIG. 7D, but may also beadapted to work with any of the embodiments illustrated in FIGS. 7A-7Cas well as additional embodiments not shown. In the embodiment shown inFIG. 7E, an extra layer of metal or other conductive material has beenused to form a bus structure 44. This allows signal routing along theback of the interferometric modulators, eliminating a number ofelectrodes that may otherwise have had to be formed on the substrate 20.

In embodiments such as those shown in FIG. 7, the interferometricmodulators function as direct-view devices, in which images are viewedfrom the front side of the transparent substrate 20, the side oppositeto that upon which the movable electrode is arranged. In theseembodiments, the reflective layer 14 optically shields some portions ofthe interferometric modulator on the side of the reflective layeropposite the substrate 20, including the deformable layer 34 and the busstructure 44. This allows the shielded areas to be configured andoperated upon without negatively affecting the image quality. Thisseparable modulator architecture allows the structural design andmaterials used for the electromechanical aspects and the optical aspectsof the modulator to be selected and to function independently of eachother. Moreover, the embodiments shown in FIGS. 7C-7E have additionalbenefits deriving from the decoupling of the optical properties of thereflective layer 14 from its mechanical properties, which are carriedout by the deformable layer 34. This allows the structural design andmaterials used for the reflective layer 14 to be optimized with respectto the optical properties, and the structural design and materials usedfor the deformable layer 34 to be optimized with respect to desiredmechanical properties.

TABLE OF CONTENTS

I. Manufacturing Interferometric Modulators through Attaching Substrates. . . 30

II. Formation of Front Substrates . . . 32

1. Formation of Shaped Front Substrate . . . 33

2. Formation of Patterned Front Substrate . . . 47

3. Formation of Preformed Support Front Substrate . . . 49

4. Other Column Routing Structures . . . 50

III. Formation of Back Carriers . . . 51

1. Shaped Carriers . . . 52

-   -   a. Shaped Carrier Backplate . . . 54    -   b. Shaped Removable Carrier . . . 64

2. Carriers with Patterned Movable Electrodes . . . 66

-   -   a. Carrier Backplate with Patterned Movable Electrodes . . . 66    -   b. Removable Carrier with Patterned Movable Electrodes . . . 69        IV. Lamination . . . 70

1. Shaped Carrier Backplate and Shaped Front Substrate . . . 71

-   -   A. Embodiment A . . . 71        -   a. Routing Option 1 . . . 72        -   b. Routing Option 2 . . . 74        -   c. Routing Option 3 . . . 75        -   d. Routing Option 4 . . . 76        -   e. Packaging and Sealing . . . 76    -   B. Embodiment B . . . 79

2. Shaped Carrier Backplate and Patterned Front Substrate . . . 80

3. Shaped Carrier Backplate and Preformed Support Front Substrate . . .80

4. Shaped Removable Carrier and Shaped Front Substrate . . . 81

5. Shaped Removable Carrier and Patterned Front Substrate . . . 82

6. Shaped Removable Carrier and Preformed Support Front Substrate . . .82

7. Carrier Backplate with Patterned Movable Electrodes and Shaped FrontSubstrate . . . 83

8. Carrier Backplate with Patterned Movable Electrodes and PatternedSubstrate . . . 84

9. Carrier Backplate with Patterned Movable Electrodes and PreformedSupport Front Substrate . . . 84

10. Removable Carrier with Patterned Movable Electrodes and Shaped FrontSubstrate . . . 85

11. Removable Carrier with Patterned Movable Electrodes and PatternedFront Substrate . . . 85

12. Removable Carrier with Patterned Movable Electrodes and PreformedSupport Front Substrate . . . 86

13. Shaped Front Substrate and Traditional Deposition of MovableElectrodes . . . 86

V. Spacers for Maintaining Space between Front Substrate and Backplate .. . 87

VI. Black Mask . . . 91

1. Patterned Black Mask . . . 92

2. Partial Wetting Black Mask . . . 93

VII. Static Interferometric Display . . . 94

1. Static Interferometric Display with Shaped or Preformed Support FrontSubstrate . . . 95

2. Static Interferometric Display with Shaped or Preformed Backplate . .. 98

3. Static Interferometric Display with Cavity Filler . . . 100

4. Static Interferometric Display with Continuous Depth Cavities . . .102

I. Manufacturing Interferometric Modulators Through Attaching Substrates

In some embodiments, MEMS devices may be made by attaching twosubstrates, each of which has components preformed thereon. In addition,the two substrates may be separately manufactured by differentmanufacturers having equipments suitable for making each substrate.Then, the substrates may be assembled together by a third manufacturer.The assembly process can also aid in reducing movable layer leeway andthus cavity size variability from MEMS component to MEMS componentacross an array, or from array to array. Such flexibility inmanufacturing not only reduces the overall costs, but also provides ahigher yield. Furthermore, some of the embodiments described hereinbelowfacilitate patterning without masking (e.g., photolithography), and canthus reduce the manufacturing costs by avoiding complicated steps tobuild up topography from multiple thin layers.

MEMS devices made by the processes described herein may have arelatively small gap (e.g., between about 6,500 Å and about 20 μm, andparticularly between about 2 μm and about 15 μm or between about 10,000Å and about 5 μm) between the two substrates thereof. In the embodimentsdescribed in this disclosure, a gap between two substrates (i.e., afront substrate and a backplate) generally refers to a gap between thebottom of the deepest trough of the front substrate and a backplatesurface facing the front substrate when the backplate overlies the frontsubstrate. The backplate surface is one which is most removed from thefront substrate. The “gap between two substrates” will be betterunderstood from description below with respect to the lamination of ashaped carrier backplate and a shaped front substrate. In addition, theMEMS devices may have supports or spacers throughout the array regionthereof, not only at their edges. Thus, the MEMS devices are lesssusceptible to pressure variations. In addition, the relatively smallgap requires less sealant between the two substrates, and thus the MEMSdevices are less susceptible to moisture leakage, even without adesiccant inside the MEMS devices. Furthermore, the MEMS devices mayhave a slim profile because of the small gap size.

In embodiments below, MEMS devices are described in the context ofoptical MEMS devices, particularly interferometric modulators. A skilledartisan will, however, appreciate that the processes described hereinhave application for other MEMS devices, such as other types of opticalMEMS or MEMS electromechanical capacitive switches.

FIG. 8 illustrates an interferometric modulator display device 800 inaccordance with one embodiment. The interferometric modulator displaydevice 800 includes a display region 801 and a peripheral region 802.

The display region 801 includes a plurality of pixels which are togetherconfigured to display an image or a sequence of images. The displayregion 801 includes row electrodes (not shown) extending substantiallyparallel to one another, and column electrodes (not shown) extendingsubstantially parallel to one another and substantially perpendicular tothe row electrodes. The row and column electrodes are verticallyseparated and together define a matrix of pixels at the intersectionsthereof.

The peripheral region 802 surrounds the display region 801. The displayregion 801 is also referred to herein as an “array region” because itincludes an array of individually actuated electrostatic MEMS units. Theperipheral region 802 may include driver chip regions and interconnector routing structures. The device 800 may have a row driver 811 and acolumn driver 812 mounted on the driver chip regions. The drivers 811and 812 may be mounted on the driver chip regions using any suitablebonding technique, including, but not limited to, chip-on-glass (COG)bonding, tape carrier package (TCP) attachment, or film-on-glass (FOG)bonding. The routing structures are configured to electrically connectthe row and column electrodes to the row and column drivers 811, 812,respectively.

The interferometric modulator display device 800 of FIG. 8 may be formedby attaching a front substrate to a backplate. FIG. 9 illustrates amethod of making an interferometric modulator display device 900according to one embodiment. First, a front substrate 910 is providedhaving a display or array region 901 and a peripheral region 902. Thefront substrate 910 may include an array of cavities or trenches in thedisplay region 901. The cavities or trenches may each include an opticalstack including fixed or stationary electrodes. The front substrate 910may also include routing structures and driver chip regions in theperipheral region 902, as described with respect to FIG. 8.

Then, a carrier 950 for carrying some functional components of theinterferometric modulator display device 900 is attached to the frontsubstrate 910, covering the display region 901 and part of theperipheral region 902 that surrounds the display region 901. In oneembodiment, movable electrodes are formed on the carrier 950 prior toattaching the carrier 950 to the front substrate 910. When the frontsubstrate 910 and carrier 950 are attached to each other, the movableelectrodes are interposed therebetween. The movable electrodes may beattached to support structures of the front substrate 910, using, forexample, anodic bonding, fusion bonding, and analogous methods.

In some embodiments, movable electrodes are formed on a carrier, whichcan be a removable carrier (see, e.g., FIGS. 35A-35D, and attendantdescription). In other embodiments the carrier serves as a permanentbackplate for the display device 900 (see, e.g., FIGS. 25-34D and36A-39B, and attendant description). In another embodiment, movableelectrodes are formed over the front substrate prior to attaching apermanent backplate to the front substrate. Then, the backplate isattached to the front substrate.

II. Formation of Front Substrates

In making the interferometric modulator display device described above,the front substrate of the device may be formed in various ways. In oneembodiment, the front substrate may be prepared by forming cavities orrecesses into a surface of a substrate, and then forming an opticalstack in the cavities. The cavities may be formed by any suitableprocess, e.g., embossing, photolithography and etching, and inscribing.In the context of this document, a front substrate formed by such aprocess is referred to as a “shaped front substrate.” Typically, thecavities are demarcated by supports (e.g., rails or posts) that areintegrally formed with the substrate for shaped front substrates.

In another embodiment, the front substrate may be prepared by forming anoptical stack on a substrate and then forming supports on the opticalstack to define cavities. In the context of this document, a frontsubstrate formed by this process is referred to as a “patterned frontsubstrate.” Typically, the supports are separate from and formed overthe substrate, and can be made of materials different from the substratefor patterned substrates. (See, e.g., FIGS. 22A-22C and attendantdescriptions).

In yet another embodiment, the front substrate may be made by formingposts on a substrate to define cavities, and then forming an opticalstack in the cavities. In the context of this document, a frontsubstrate formed by this process is referred to as a “preformed supportfront substrate.” Like a patterned front substrate, preformed supportfront substrates have posts separately from the substrate and can bemade of material different from the substrate; unlike patterned frontsubstrates, the optical stacks (including stationary electrodes) are notinterposed between the supports and the substrate.

1. Formation of Shaped Front Substrate

FIG. 10 is a schematic partial perspective view of a shaped frontsubstrate 1000 according to one embodiment. The illustrated portion ofthe front substrate 1000 is part of the display region of the frontsubstrate 1000. Therefore, it should be noted that FIG. 10 is only apartial illustration of the display region and thus the structure shownin FIG. 10 is repeated substantially throughout the display region.

The front substrate 1000 includes a substrate 1010 having a plurality ofrails 1011 a-1011 d and a plurality of troughs 1012 a-1012 c definedbetween pairs of the rails 1011 a-1011 d. The substrate 1010 alsoincludes a plurality of posts 1013 a-1013 c formed in the troughs 1012a-1012 c. In the context of this document, the rails 1011 a-1011 d andthe posts 1013 a-1013 c may be collectively referred to as “supports” or“support structures.” The front substrate 1000 also includes opticalstacks 1014 (which include stationary electrodes) on the bottom of thetroughs 1012 a-1012 c and the same layers of the optical stacks 1014 ontop of the supports 1011 a-1011 d and 1013 a-1013 c.

The substrate 1010 may be formed of a substantially transparentmaterial. Examples of the transparent material include, but are notlimited to, glass and transparent polymeric materials. In otherembodiments for non-optical MEMS devices, the substrate may include astainless steel plate laminated with a polymeric material (e.g.,polyethylene). The substrate 1010 may be shaped by any method suitablefor removing or shaping portions of the substrate 1010 or formingrecesses into a surface of the substrate 1010. Examples of shapingmethods include, but are not limited to, embossing, photolithography andetching, and inscribing. Because the substrate 1010 is shaped withoutadding an additional material to the substrate 1010 in the methodsdescribed above, the supports in the form of the rails 1011 a-1011 d andthe posts 1013 a-1013 c may be formed integrally with and of the samematerial as that of the substrate 1010.

The rails 1011 a-1011 d extend in a row direction (x-direction) parallelto one another, as shown in FIG. 10. It will be understood thatdesignation of row/column or XYZ directions are essentially arbitrary,but will be referenced consistently herein. The rails 1011 a-1011 d havetheir top surfaces at substantially the same level, i.e., within asingle plane.

The troughs 1012 a-1012 c alternate with the rails 1011 a-1011 d,extending in the row direction (x-direction) parallel to one another, asshown in FIG. 10. The troughs 1012 a-1012 c provide cavities or spacesfor movable electrodes (not shown) to collapse down towards the frontsubstrate 1010, as will be better understood from description below.

For the illustrated interferometric modulator embodiment, the troughs1012 a-1012 c may have a depth between about 600 Å and about 4,000 Å.The troughs 1012 a-1012 c may have various depths D1, D2, D3, dependingon the colors which the troughs 1012 a-1012 c are designed to produceduring operation of the resulting display device. In the illustratedembodiment, the front substrate 1000 has first, second, and thirdtroughs of three different depths D1, D2, D3 for three different colors.The first trough 1012 a has the smallest depth and is configured togenerate blue (B) color. The first trough 1012 a may have a first depthD1 between about 600 Å and about 2,000 Å. The second trough 1012 b hasan intermediate depth and is configured to generate green (G) color. Thesecond trough 1012 b may have a second depth D2 between about 1,000 Åand about 3,000 Å. The third trough 1012 c has the greatest depth, andis configured to generate red (R) color. The third trough 1012 c mayhave a third depth D3 between about 2,000 Å and about 4,000 Å. Thetroughs 1012 a-1012 c may have a width W between about 10 μm and about200 μm. A skilled artisan will appreciate that the configurations anddepths of the troughs 1012 a-1012 c may vary depending on the colors anddesigns of pixels.

The posts 1013 a-1013 c are formed on the bottom of the troughs 1012a-1012 c, extending upward. The posts 1013 a-1013 c have their topsurfaces at substantially the same level (substantially in the sameplane) as the tops of the rails 1011 a-1011 d. Each post 1013 a-1013 chas a height which corresponds to the depth of the trough 1012 a-1012 cin which the post 1013 a-1013 c is positioned. Thus, the posts 1013a-1013 c in the troughs 1012 a-1012 c of different depths have heightsdifferent from one another. In the illustrated embodiment, the posts1013 a in the first trough 1012 a have a first height corresponding tothe first depth D1. The posts 1013 b in the second trough 1012 b have asecond height corresponding to the second depth D2. The posts 1013 c inthe third trough 1012 c have a third height corresponding to the thirddepth D3.

The posts 1013 a-1013 c are arranged in a predetermined pattern. As willbe better understood from description below, the illustrated portion ofthe display region of the front substrate 1000 forms a single pixel Pwhich may be replicated across the entire display region in a matrixform. The illustrated pixel P has a substantially square form. The pixelP includes a first subpixel SP1, a second subpixel SP2, and a thirdsubpixel SP3, each of which is in a rectangular form. Each of thesubpixels SP1-SP3 includes sub-subpixels SSP11-SSP13, SSP21-SSP23, orSSP31-SSP33. Each sub-subpixel SSP11-SSP13, SSP21-SSP23, SSP31-SSP33includes a group of four posts to provide support for a movableelectrode (not shown). The posts 1013 a-1013 c are spaced apart from oneanother to allow the movable electrode to bend down therebetween. In theillustrated embodiment, each of the sub-subpixels SSP13, SSP21-SSP23,SSP31-SSP33 has four posts positioned near free edges of thesub-subpixel when viewed from above.

The optical stacks 1014 may include several fused layers. In oneembodiment, the optical stacks 1014 may include a transparent conductivelayer and a dielectric layer overlying the transparent conductive layer.The transparent conductive layer may be formed of indium tin oxide(ITO). The dielectric layer may be formed of silicon dioxide. In anotherembodiment, the dielectric layer may have a two-layered structure,including an upper sublayer and a lower sublayer. In certain embodimentsin which the dielectric layer is exposed to a fluorine etchant for anysacrificial layer release steps, the upper sublayer may be formed of aprotective material such as aluminum oxide. The lower sublayer may beformed of silicon dioxide. In one embodiment, the transparent conductivelayer may have a thickness between about 10 Å and about 800 Å. Thedielectric layer may have a thickness between about 100 Å and about1,600 Å. In the embodiment in which the dielectric layer has upper andlower sublayers, the upper sublayer may have a thickness of, forexample, about 50 Å, while the lower sublayer may have a thickness of,for example, about 450 Å. In the illustrated embodiment, the opticalstacks 1014 are discontinuous between the bottom of the troughs 1012a-1012 c and the top of the supports 1011 a-1011 d and 1013 a-1013 c.

The conductive layers of the optical stacks 1014 on the bottom of thetroughs 1012 a-1012 c are electrically isolated from one another by therails 1011 a-1011 d. The electrically isolated conductive layers formrow electrodes of the resulting interferometric modulator displaydevice.

In certain embodiments, the optical stacks 1014 may also include ametallic absorber layer (or a partially reflective layer) between thetransparent conductive layer and the dielectric layer. The absorberlayer may be formed of a semi-transparent thickness of metal, such aschromium (Cr), molybdenum (Mo), or Mo/Cr. In another embodiment for abroad-band white interferometric modulator, the absorber layer may bereplaced with a semiconductor layer, such as a germanium layer. Theabsorber or semiconductor layer may have a thickness between about 1 Åand about 100 Å, particularly between about 50 Å and about 100 Å.

FIG. 11A is a cross section of the front substrate 1000 (without theoptical stacks 1014) of FIG. 10, taken along the lines 11A-11A. Becauseof the difference in the depths, the troughs 1012 a-1012 c have theirbottom surfaces at different levels, L1 a, L1 b, L1 c, respectively.However, because the supports 1011 a-1011 d and 1013 a-1013 c havedifferent heights corresponding to the depths of the troughs 1012 a-1012c, the top surfaces of the supports 1011 a-1011 d and 1013 a-1013 c areat substantially the same level L2, i.e., substantially in the sameplane.

Optical stacks on top of the supports 1101 a-1101 d, 1013 a-1013 c canserve as “black masks.” The optical stacks provide the same opticaleffect at all times as interferometric modulators in their collapsedstate. The optical stacks can provide black color. In other embodiments,the optical stacks can provide white color, depending on theinterferometric modulator design.

FIG. 11B is the cross section of FIG. 11A, after deposition of theoptical stacks 1014. Because of the optical stacks 1014, the uppermostpoint of the front substrate 1000 is at a level L2′ which is higher thanthe level L2 by the thickness of the optical stacks 1014.

FIGS. 12A-12D are cross sections illustrating a method of forming ashaped front substrate according to one embodiment. The illustratedmethod uses embossing for shaping the front substrate. As shown in FIG.12A, a substantially flat substrate 1210 is placed on a platen 1220. Thesubstrate 1210 may be formed of glass or other material, preferablytransparent, that is readily made malleable for shaping. The illustratedplaten 1220 may be formed of a metallic material. The substrate 1210 maybe heated such that the substrate 1210 is soft enough to impress at asubsequent embossing step. The substrate 1210 may be heated to atemperature which varies depending on the material used for thesubstrate 1210.

Then, an embossing plate 1230 is pressed onto the softened substrate1210, as shown in FIG. 12B. The embossing plate 1230 has recesses andprotrusions shaped to define rails, troughs, and posts on the substrate1210. The embossing plate 1230 may be formed of a metallic material. Incertain embodiments, at least one of the platen 1220 and the embossingplate 1230 may be in a form of a rotating cylinder. A skilled artisanwill appreciate that various other configurations of embossingtechniques may also be adapted for shaping the front substrate 1210.

Then, the embossing plate 1230 is removed from the front substrate 1210.Subsequently, the embossed front substrate 1210 is removed from theplaten 1220. The resulting front substrate 1210 is shown in FIG. 12C.

In another embodiment, the front substrate 1210 may be shaped byselectively removing portions of a substrate using photolithography andetching technique. In yet another embodiment, the front substrate 1210may be shaped by first inscribing predetermined portions of a substrateand then selectively etching the portions. The term “inscribing” may beused interchangeably with marking or scoring. Inscribing may beconducted using various techniques, e.g., machining or laser-inscribing.An automatic inscribing method is available from Nippon Sheet Glass,Co., Ltd, Tokyo, Japan. The embossing technique shown in FIGS. 12A-12Dcan be conducted without a masking process. In addition, a patternedplate can be repeatedly used for many substrates. It will be appreciatedthat various other techniques may also be used for shaping the frontsubstrate 1210.

Subsequently, optical stack materials are sequentially depositedsubstantially across the shaped front substrate 1210. The optical stackmaterials can be deposited using any suitable technique, e.g.,sputtering, such that the optical stack 1214 is deposited on the tops ofsupports and on the bottoms of troughs, but is not conformal enough forcontinuous sidewall coverage. This configuration can apply to any MEMSdevice (optical or non-optical MEMS device). The optical stacks on topof the supports can serve as a “black mask” for an optical MEMS device.The configuration of the optical stacks 1214 may be as described abovewith respect to the optical stacks 1014 of FIG. 10.

FIG. 13 is a partial perspective view of one embodiment of a partiallyfabricated interferometric modulator display device 1300 including afront substrate 1310 with movable electrodes 1360 arranged thereon. Theconfiguration of the front substrate 1310 may be as described above withrespect to the front substrate 1000 of FIG. 10. The movable electrodes1360 run substantially parallel to one another and substantiallyperpendicular to troughs 1312 a-1312 c of the front substrate 1310, asshown in FIGS. 13 and 14A. In the illustrated embodiment, the movableelectrodes 1360 and the troughs 1312 a-1312 c intersect with each other,defining sub-subpixels described above with reference to FIG. 10. Inother embodiments, a single movable electrode (instead of the threemovable electrodes 1360 of FIG. 13) may cover substantially the entireillustrated portion of the front substrate 1310, thereby defining asingle pixel.

In the embodiment of FIGS. 13, and 14A-14C, the movable electrodes 1360are supported on rails 1311 a-1311 c and posts 1313 a-1313 c of thefront substrate 1310 with intervening optical stacks 1314 a, as shown inFIGS. 13 and 14B (a cross section of the device of FIG. 13, taken alonglines 14B-14B). FIG. 14C (another cross section of the device of FIG.13, taken along lines 14C-14C) also illustrates that the movableelectrodes 1360 are supported on the posts 1313 a-1313 c of the frontsubstrate 1310 with the intervening optical stacks 1314 a. In certainembodiments, edge spacers 1315 (FIG. 14A) may be provided on the bottomof the troughs 1312 a-1312 c to further support the movable electrodes1360. The edge spacers 1315 may be positioned at edges of each pixelwhile being laterally spaced from the posts 1313 a-1313 c.

FIG. 14D is a partial enlarged cross-section of the front substrate 1310of FIG. 14B with a movable electrode 1360 formed thereon. The movableelectrode 1360 is supported on top of the optical stacks 1314 a on thesupport structures (e.g., the rails 1311 a-1311 c and the posts 1313a-1313 c) of the front substrate 1310. The illustrated movable electrode1360 has first portions Ma overlying the support structures and secondportions Mb between the first portions Ma. The second portions Mb do notoverlie the support structures. The first portions have a firstthickness T1 while the second portions have a second thickness T2.

As described above with reference to FIG. 9, the movable electrode 1360is formed on a carrier prior to being attached to the front substrate1310. In order to attach the movable electrode 1360 to the frontsubstrate 1310, the carrier is pressed against the front substrate 1310with the movable electrode 1360 interposed therebetween. Portions (e.g.,the first portions Ma described above) of the movable electrode 1360which contact the support structures may be compressed, particularlywhere the movable electrode 1360 is deformable or malleable. As aresult, the first thickness T1 of the first portions Ma of the movableelectrode 1360 may be thinner than the second thickness T2 of the secondportions Mb thereof. In one embodiment, the first thickness T1 may befrom about 200 Å to about 2,000 Å. The second thickness T2 may be fromabout 200 Å to about 2,000 Å. A difference between the first thicknessT1 and the second thickness T2 may be from about 5 Å to about 100 Å. Thedifference between the first and second thicknesses T1 and T2 can varydepending on the pressure applied when attaching the movable electrode1360 to the front substrate 1310.

Returning to FIG. 13, the illustrated movable electrodes 1360 areelongated or strip-shaped, each spanning multiple MEMS units or pixelsin a column. The elongated movable electrodes 1360 may have a length anda width. A ratio of the length to the width of the movable electrodes1360 is roughly on the same order as about x:1 where x is three timesthe number of pixels in a column across a display array. In oneembodiment, the length-to-width ratio of the movable electrodes 1360 isbetween about 10:1 and about 1,000,000:1. The movable electrodes 1360may include a reflective layer (or mirror) 1360 a and a mechanical (ordeformable) layer 1360 b. The reflective layer 1360 a may be attached orfused to the mechanical layer 1360 b; in other arrangements, thereflective layer may be suspended from the mechanical layer (see, e.g.,FIGS. 7C-7E). The reflective layer 1360 a may be formed of a specular orreflective metal, for example, Al, Au, Ag, or an alloy of the foregoing,and is thick enough to reflect substantially all visible light incidentupon the front substrate 1310 for interferometric effect. The mechanicallayer 1360 b may be formed of Ni, Cu, Pt, Au, Al, or an alloy of theforegoing. The mechanical layer 1360 b may have a thickness that issufficient to provide mechanical support while being sufficiently thinand flexible to allow the movable electrodes 1360 to move toward theoptical stacks 1314 b on the bottom of the troughs 1312 a-1312 c. Themechanical layer 1360 b may have a thickness between several hundredangstroms and several thousand angstroms. In an exemplary embodiment,the reflective layer 1360 a has a thickness of about 300 Å, and themechanical layer 1360 b has a thickness of about 1000 Å. The thicknessesof the layers 1360 a and 1360 b may be different in other embodiments.In certain embodiments where the MEMS device is used as anelectromechanical capacitive switch, the movable electrodes may includea substantially electrically conductive material.

FIG. 15 is a schematic top plan view of the partially fabricatedinterferometric modulator display device 1300 of FIG. 13. The device1300 includes the front substrate 1310 and the plurality of movableelectrodes 1360 formed thereon.

The front substrate 1310 includes a display region 1301 and a peripheralregion 1302. The front substrate 1310 includes a plurality of troughs1312 extending parallel to one another in the display region 1301, thetroughs including stationary electrodes at their bottoms. The frontsubstrate 1310 also includes a plurality of routing trenches 1316R,1316C and driver chip regions 1303 a, 1303 b in the peripheral region1302. The routing trenches include row routing trenches 1316R and columnisolation trenches 1316C. The driver chip regions include a row driverchip region 1303 a and a column driver chip region 1303 b. The movableelectrodes 1360 run substantially parallel to one another andsubstantially perpendicular to the troughs 1312 of the front substrate1310.

FIG. 16A is a top plan view of the front substrate 1310 of FIG. 15 withthe position of just one movable electrode 1360, shown in phantom. Asdescribed above, the front substrate 1310 includes the troughs 1312 inthe display region 1301 and the row routing trenches 1316R and thecolumn isolation trenches 1316C in the peripheral region 1302. The rowrouting trenches 1316R extend from the troughs 1312 to the row driverchip region 1303 a. The column isolation trenches 1316C extend from nearthe display region 1301 to the column driver chip region 1303 b suchthat one end of each trench is proximate to a corresponding one of themovable electrodes 1360.

FIG. 16B is an enlarged top plan view of one of the troughs 1312 and acorresponding one of the row routing trenches 1316R of FIG. 16A, denotedby 16B. The trough 1312 has a width W1. The row routing trench 1316R hasa width W2 smaller than the width W1 of the trough 1312. The frontsubstrate 1310 also includes a contact trench 1317 connected to the rowrouting trench 1316R. The contact trench 1317 is shaped to accommodate aconnecting bump or anisotropic conductive film (not shown) of a rowdriver which will provide electrical signals to the pixels of theresulting interferometric modulator display device. While illustrated assquare or rectangular in FIG. 16B, in other embodiments, the frontsubstrate 1310 may have contact trenches of various other shapes andconfigurations. The trough 1312, the row routing trench 1316R, and thecontact trench 1317 have substantially the same depth D, as shown inFIG. 16C. In other embodiments, one of the trough 1312, the row routingtrench 1316R, and the contact trench 1317 may have a different depthfrom the others. Referring to FIG. 16D, in another embodiment, therouting trench 1316R may have a decreasing depth D2 or ramped bottom asit extends from the trough 1312 to the contact trench 1317. In anembodiment in which the substrate is shaped by inscribing, such a depthvariation can be made by varying pressure during inscribing. It will beappreciated that the depths and widths of the trough 1312, the rowrouting trench 1316R, and the contact trench 1317 may vary widelydepending on the structure and dimension of the front substrate 1310 anddriver chips provided thereto.

FIG. 16E is a cross section of the bare front substrate 1310 of FIG. 16Cafter processing to form the optical stacks 1314 a, 1314 b with a rowdriver 811 mounted thereon. The driver 811 includes a plurality ofelectrical leads 811 a facing downward as shown in FIG. 16E. Theillustrated portion of the front substrate 1310 includes the row routingtrench 1316R and the contact trench 1317. The front substrate 1310 alsoincludes optical stacks 1314 a, 1314 b on top of the peripheral regionand on the bottom of the row routing trench 1316R. The optical stack1314 b on the bottom of the row routing trench 1316R includes adielectric layer 1314 b 1 and an underlying conductive layer 1314 b 2.The configuration of the optical stack 1314 b may be as described abovewith respect to the optical stacks 1014 of FIG. 10. The conductive layer1314 b 2 extends into the contact trench 1317 while the dielectric layer1314 b 1 does not. This configuration exposes the conductive layer 1314b 2 in the contact trench 1317, and thus allows electrical connectionbetween the conductive layer 1314 b 2 and a corresponding one of theleads 811 a of the row driver 811. A variety of techniques can be usedfor exposing the conductor 1314 b 2 in the contact trench 1317,including shadow mask techniques described below with respect to FIGS.20 and 21.

In the illustrated embodiment, the electrical connection is provided byan anisotropic conductive film (ACF). The ACF includes conductiveparticles 813 dispersed in a polymeric or organic film (not shown). Inestablishing the electrical connection, the ACF is interposed betweenthe pad formed by the conductive layer 1314 b 2 in the contact trench1317 and the lead 811 a of the driver 811. Then, the driver 811 ispressed against the front substrate 1310, optionally with heat to atleast partially cure the film. One or more of the conductive particles813 in the polymeric film provide electrical connection by contactingboth the conductive layer 1314 b 2 and the lead 811 a of the driver 811.But between contact trenches 1317 (see plan view of FIG. 16A), theconductive particles across the ACF are insulated from one another bythe polymeric matrix, preventing driver leads 811 a or contact pads inregions 1317 from shorting to one another. A skilled artisan willappreciate that various types of ACFs may be adapted for providing theelectrical connection. A skilled artisan will also appreciate thatvarious other bonding techniques may also be used for providing theelectrical connection.

FIG. 17A illustrates one embodiment of a column routing structure of aninterferometric modulator display device 1700. The illustrated displaydevice 1700 includes a front substrate 1710 having rails 1711 andtroughs 1712 in its display region or array 1701 and column isolationtrenches 1716C in its peripheral region 1702. The illustrated portion ofthe peripheral region 1702 of the front substrate 1710 has a top surfaceat a higher level relative to the bottom of the troughs 1712. The topsurface of the peripheral region 1702 may be at the same level as thoseof the rails 1711.

The front substrate 1710 also includes optical stacks 1714 a, 1714 bthat have been simultaneously deposited on the top surface of theperipheral region 1702 and on the bottom of the isolation trenches 1716Cand the troughs 1712. The optical stacks 1714 a, 1714 b include adielectric layer 1714 a 1, 1714 b 1 and a conductive layer 1714 b 1,1714 b 2 underlying the dielectric layer 1714 a 1, 1714 b 1. Theconfiguration of the optical stacks 1714 a, 1714 b may be as describedabove with respect to the optical stacks 1014 of FIG. 10. It will beunderstood that the optical stacks 1714 b in the troughs 1712 serve asstationary electrodes for the MEMS device.

The device 1700 also includes movable electrodes 1760 overlying thefront substrate 1710 and extending substantially perpendicular to thetroughs 1712. The movable electrodes 1760 extend from the display region1701 to an elevated portion of the peripheral region 1702.

The column isolation trenches 1716C define a plurality of lands or mesas1716M alternating with the trenches 1716C. The trenches 1716C extendfrom near the display region 1701 to a driver chip region (not shown)for a column driver (not shown) distal from the display region 1701. Thecolumn isolation trenches 1716C are configured to provide electricalisolation between the optical stacks 1714 a on top of the mesas 1716Mwithout additional patterning. Each of the trenches 1716C completelysurrounds a corresponding one of the mesas 1716M. The column isolationtrenches 1716C also have a depth sufficient to allow the optical stacks1714 a, 1714 b to be discontinuous between the mesas 1716M and thecolumn isolation trenches 1716C when optical stack materials aredeposited across the shaped front substrate 1710 as described above withrespect to FIG. 12D. The conductive layer 1714 a 2 of each of theoptical stacks 1714 a on the mesas 1716M provides electrical connectionbetween one of the movable electrodes 1760 and a corresponding one ofthe pads of the column driver (not shown). The conductive layers 1714 a2 electrically isolated from one another on the mesas 1716M may bereferred to as “routing traces” or “conductive traces.”

In one embodiment, the column isolation trenches 1716C may have a depthgreater than the depth of the troughs 1712. However, it will beappreciated that the depth of the column isolation trenches 1716C mayvary widely depending on the other dimensions of the front substrate1710, conformality of the stationary electrode deposition, and othercomponents of the interferometric modulator display device 1700.

FIG. 17B is a cross section of the device 1700, taken along lines17B-17B of FIG. 17A. In the illustrated embodiment, the conductivetraces 1714 a 2 are formed on the top surface of the front substrate1710 at level L2 a. The top surface of the conductive traces 1714 a 2 isat level L2 b. The dielectric layer 1714 a 1 is formed on the conductivetraces 1714 a 2 while exposing portions of the conductive traces 1714 a2 so as to permit electrical connection between the conductive traces1714 a 2 and end portions of the movable electrodes 1760 extending tothe peripheral region 1702.

In order to expose the portions of the conductive traces 1714 a 2, theoverlying dielectric layer 1714 a 1 may be patterned using any suitableprocess. In one embodiment, the dielectric layer 1714 a 1 may bepatterned using photolithography and etching. In another embodiment, ashadow mask may be used to cover the portions of the conductive traces1714 a 2 when depositing the dielectric layer 1714 a 1 such that nodielectric layer is formed on the portions of the conductive traces 1714a 2. The details of using shadow masks are described in more detailbelow with respect to FIGS. 20, 21, 44A-44E. The movable electrodes 1760have bottom surfaces at level L2 c which is higher than the level L2 b.Thus, there exists a gap between the bottom surfaces of the movableelectrodes 1760 at the level L2 c and the top surface of the conductivetraces 1714 a 2 at the level L2 b. The gap may interfere with reliableelectrical connection between the conductive traces 1714 a 2 and themovable electrodes 1760, particularly when the movable electrodes arelaminated onto the front substrate 1710.

In the illustrated embodiment, gap-fillers 1717 are provided to fill thegap between the conductive traces 1714 a 2 and the movable electrodes1760, and establish electrical connection therebetween. The gap-fillers1717 may be formed of a conductive adhesive material. Thus, thegap-fillers 1717 may also serve to attach the movable electrodes 1760 tothe conductive traces 1714 a 2. The adhesive material may be a cold-weldmaterial which may be weldable at a relatively low temperature. Examplesof the material include, but are not limited to, antimony (Sb), indium(In), or tin (Sn). The material may be soft and deformable. A skilledartisan will appreciate that various other materials (e.g., an ACF) mayalso be used for the gap-fillers 1717.

FIG. 17C is a cross section of the device 1700, taken along lines17C-17C of FIG. 17A. FIG. 17C shows a routing region 1702A and anon-routing region 1702B of the peripheral region 1702 of the device1700. The illustrated cross section specifically shows a portion of therouting region 1702A where the movable electrodes 1760 (one shown) areconnected to the conductive traces 1714 a 2. In the routing region1702A, the column isolation trenches 1716C are formed to define themesas 1716M. On top of the conductive layer 1714 a 2 on the mesas 1716Mare the gap-fillers 1717. On the other hand, in the non-routing region1702B which has no column isolation trenches, both a conductive layer1714 a 2 and a dielectric layer 1714 a 1 are stacked on top of the frontsubstrate 1710.

FIG. 18A illustrates another embodiment of a column routing structure ofan interferometric modulator display device 1800. The display device1800 includes a front substrate 1810 having troughs 1812 in its displayregion 1801, but no column isolation trenches in the peripheral region1802 thereof. The front substrate 1810 also includes optical stacks 1814a, 1814 b formed thereon. The optical stacks 1814 a, 1814 b include adielectric layer 1814 a 1, 1814 b 1 and a conductive layer 1814 a 1,1814 b 1 underlying the dielectric layer 1814 a 1, 1814 b 1. The opticalstacks 1814 a, 1814 b may be blanket deposited across the frontsubstrate 1810 as illustrated in FIG. 12D.

The front substrate 1810 further includes column routing traces 1817 onthe dielectric layer 1814 a 1 in the peripheral region 1802. The routingtraces 1817 are configured to electrically connect movable electrodes1860 to the pads of a column driver (not shown). Each of the routingtraces 1817 includes a contact portion 1817 a and a routing portion 1817b. In the illustrated embodiment, the contact portion 1817 a is widerthan the routing portion 1817 b to facilitate electrical contact with amovable electrode 1860. Although not shown, the distal end of therouting traces 1817 may have contact pad portions shaped similar to thecontact portion 1817 a. Unlike the conductive traces 1714 a 2 of FIG.17B, the routing traces 1817 are on top of the optical stack 1814 a.Therefore, no gap-filler is employed for electrical connection betweenthe routing traces 1817 and the movable electrodes 1860. Referring toFIG. 18C, the routing traces 1817 are formed only in the routing region1802A of the peripheral region 1802 of the front substrate 1810, but notin the non-routing region 1802B thereof. The routing traces 1817 may beformed by any suitable method, for example, screen or Gravue printing orphotolithography and etching. Column routing is provided at a higherlevel (the substrate level of supports and the substrate level of themovable electrodes). This configuration allows the movable electrodes toeasily make contact with the routing traces, particularly whenlaminating the front substrate with a carrier carrying the movableelectrodes.

FIG. 19 illustrates yet another embodiment of a column routing structurefor an interferometric modulator display device. In the illustratedembodiment, a carrier 1950, configured for joining to a front substratethat has stationary electrodes patterned on it, is provided with movableelectrodes (or strips) 1960 and column routing traces 1917. The columnrouting traces 1917 may be formed simultaneously with the movableelectrodes 1960 on the carrier 1950. Then, the carrier 1950 is placedonto a shaped front substrate (not shown) such that the movableelectrodes 1960 and the column routing traces 1917 are interposedtherebetween. Subsequently, the carrier 1950 is removed, leaving themovable electrodes 1960 and the column routing traces 1917 on the frontsubstrate. Then, the column routing traces 1917 may be used toelectrically connect the movable electrodes 1960 to the leads orcontacts of a column driver (not shown).

FIG. 20 illustrates one embodiment of a method employing shadow maskingfor depositing an optical stack on a shaped front substrate 2010.Referring back to FIG. 16E, the dielectric layer 1314 b 1 is patternedand etched, or deposited through a shadow mask, to expose the underlyingconductive layer 1314 b 2 for electrical connection between theconductive layer 1314 b 2 and the lead 811 a of the row driver 811.Referring back to FIG. 17B, the dielectric layer 1714 a 1 is patternedand etched, or deposited through a shadow mask, to expose the underlyingconductive traces 1714 a 2 for electrical connection between theconductive traces 1714 a 2 and the corresponding movable electrodes1760. Although not shown in FIG. 17B, the dielectric layer 1714 a 1 mayalso be patterned and etched, or deposited through a shadow mask, toexpose the underlying conductive traces 1714 a 2 for electricalconnection between the conductive traces 1714 a 2 and the leads orcontacts of a column driver (not shown).

Referring again to FIG. 20, the structures described above may be formedby first blanket depositing a conductive layer across the shaped frontsubstrate 2010. The conductive layer is deposited on differentelevations with poor conformality. Thus, the conductive layer isdiscontinuous over sidewalls of supports and mesas. As a result, rowelectrodes are patterned in trenches while column routing traces arepatterned on mesas. Then, shadow masks 2020 a-2020 c are placed onportions of the front substrate 2010 where the conductive layer is to beexposed in order to make contact with other elements to be mounted(e.g., column/row drivers, laminated movable electrodes). Then, adielectric material is blanket deposited across the front substrate2010. This shadow masking method may also be used for the embodimentshown in FIGS. 18A-18C to expose the conductive layer of the opticalstack in the troughs for connection between the conductive layer and thepads of a row driver. In such an embodiment, only one shadow mask willbe required in region 2020 a (FIG. 20) because the routing traces 1817are formed on the dielectric layer 1814 a 1 and thus are already exposedto the movable electrodes 1860 and the leads of the column driver. Itwill be appreciated that various other patterning techniques may also beemployed for forming the structures described above.

FIG. 21 illustrates one embodiment of a method of forming thegap-fillers 1717 of FIG. 17B. After the dielectric material is depositedon the front substrate 2010 as described above with reference to FIG.20, the shadow masks 2020 a-2020 c are removed. Then, another shadowmask 2120 is provided over the front substrate 2010, as shown in FIG.21. This shadow mask 2120 includes a plurality of openings 2121 forexposing regions where the gap-fillers are to be formed. Then, aconductive adhesive material is deposited through the openings 2121 onthe front substrate 2010, thereby forming the gap-fillers. It will beappreciated that various other methods may be used for forming thegap-fillers.

2. Formation of Patterned Front Substrate

FIGS. 22A-22C are schematic cross sections illustrating a method ofmaking a patterned front substrate according to one embodiment. In theillustrated embodiment, a substantially flat substrate 2210 is provided.Subsequently, a conductive layer 2214 b 2 is first deposited on thefront substrate 2210, and then is patterned to define row electrodes inthe display region 2201 of the front substrate 2210, as shown in FIG.22A. The row electrodes can also be patterned to extend continuously toa row driver mounted on a portion of the peripheral region 2202 of thefront substrate. In addition, the conductive layer 2214 b 2 in theperipheral region 2202 is patterned to provide column routing traces2220 for electrical connection between movable electrodes (not shown)and the leads of a column driver (not shown). In another embodiment,this step may be carried out using shadow masks similar to those shownin FIGS. 20 and 21.

Then, a dielectric layer 2214 b 1 is formed across the front substrateover the conductive layer 2214 b 2, as shown in FIG. 22B. The conductivelayer 2214 b 2 and the dielectric layer 2214 b 1 together form anoptical stack 2214. The dielectric layer 2214 b 1 may be patterned afterdeposition to provide through-holes or vias 2215 to expose theunderlying conductive layer 2214 b 2, particularly in the peripheralcolumn routing trace region 2220. This step may alternatively be carriedout using shadow masks similar to those shown in FIGS. 20 and 21 whenthe dielectric layer 2214 b 1 is deposited on the conductive layer 2214b 2.

Subsequently, insulating posts 2213 are formed on the optical stack 2214in the display region 2201. The insulating posts 2213 in the displayregion are formed of an insulating material and will serve to supportthe movable electrodes. After or prior to forming the insulating posts2213, conductive posts 2216 are formed through the through-holes 2215 inthe peripheral region 2202, as shown in FIG. 22C. The conductive posts2216 will provide electrical connection between the movable electrodes(not shown) and the column routing traces 2220, which are at differentlevels. It will be appreciated that the patterned front substrate 2200may be prepared using any suitable deposition and etching techniques.

In another embodiment, an elevated land may be formed in the peripheralregion 2202 of the front substrate 2210 to raise the column routingtraces to the level of the movable electrodes. The elevated land may beformed by forming a patterned insulating material, such as bydeposition, photolithography and etching, or depositing using a shadowmask, prior to depositing the column routing traces. In such anembodiment, no conductive posts are required. A skilled artisan willappreciate that various other techniques may be used for the routing ofthe patterned front substrate.

3. Formation of Preformed Support Front Substrate

FIGS. 23A-23C are schematic cross sections illustrating a method ofmaking a preformed support front substrate 2300 according to oneembodiment. In one embodiment, a substantially flat substrate 2310 isprovided. Then, insulating supports 2313 are formed directly on thesubstrate 2310 in the array or display region 2301. The insulatingsupports 2313 are formed of an insulating material, and may take theshape of posts, rails, walls, etc. The insulating supports 2313 willserve to support the movable electrodes (not shown). In one embodiment,the insulating supports 2313 may be formed by blanket depositing aspin-on-glass (SOG) material or oxide and patterning and etching, suchas by conventional photolithography. After or prior to forming theinsulating supports 2313, conductive supports 2316 are formed in theperipheral region 2302. The front substrate with the supports 2313, 2316is shown in FIG. 23A. While the insulating posts 2313 can be formed ofan oxide material similar to that of the glass substrate, the posts 2313material will generally be distinguishable from the substrate 2310 andan identifiable interface 2320 is formed between the insulating posts2313 and the substrate 2310.

Then, an optical stack 2314 is formed across the front substrate 2310.In forming the optical stack 2314, a conductive layer 2314 b 2 is firstdeposited on the front substrate 2310, and then is patterned to definerow electrodes in the display region 2301 of the front substrate 2310,as shown in FIG. 23B. The row electrodes can also be patterned to extendcontinuously to a row driver mounted on a portion of the peripheralregion 2232 of the front substrate 2310. In addition, the conductivelayer 2314 b 2 in the peripheral region 2302 is patterned to providecolumn routing traces for electrical connection between movableelectrodes (not shown) and the pads for mounting the column driver (notshown). In addition, a conductive layer 2314 a 2 is formed on theinsulating supports 2313 and the conductive supports 2316.

Then, dielectric layers 2314 a 1, 2314 b 1 are formed across thesubstrate 2310 over the conductive layers 2314 a 2, 2314 b 2, as shownin FIG. 23C. The formation of a dielectric layer on top of theconductive supports 2316 may be avoided by using any suitable technique,e.g., shadow masking. This configuration allows the conductive layer2314 a 2 on top of the conductive supports 2316 to interconnect withmechanical layers (not shown). A skilled artisan will appreciate thatthe preformed support front substrate 2300 may be prepared using anysuitable deposition and etching techniques.

In an interferometric modulator display device structure resulting fromthe method described in connection with FIGS. 23A-23C, the insulatingsupports are on the front substrate without an intervening optical stack(conductor and/or dielectric). The insulating supports are neitherintegral with nor formed of the same material as the substrate.

In another embodiment, an elevated land may be formed in the peripheralregion 2302 of the front substrate 2310 to raise the column routingtraces to the level of the movable electrodes, as discussed with respectto the shaped substrate of FIG. 18A. The elevated land of a preformedsupport front substrate may be formed by depositing an insulatingmaterial using a shadow mask. In such an embodiment, no conductive postsare employed. A skilled artisan will appreciate that various othertechniques may be used for the routing of the preformed support frontsubstrate.

4. Other Column Routing Structures

FIGS. 24A and 24B illustrate other embodiments of column routingstructures for either a patterned or a preformed support frontsubstrate. In the illustrated embodiments, the front substrates can beformed similar to the methods described above with reference to FIGS.22A-22C and 23A-23C except that the conductive posts are not formed inthe peripheral regions of the front substrates.

Referring to FIG. 24A, a carrier 2450 a, configured to join with a frontsubstrate having stationary electrodes, is provided with movableelectrodes 2460 a. In addition, conductive posts 2416 a are formed onthe movable electrodes 2460 a. The conductive posts 2416 a may be formedusing any suitable technique, including but not limited to,photolithography and etching, printing, and sputtering. The carrier canbe removable or sacrificial, existing to transfer the movable electrodesto the front substrate, or can serve as a permanent backplate for theMEMS device. The carrier 2450 a is laid over a front substrate 2410 asuch that the conductive posts 2416 a are interposed between the movableelectrodes 2460 a on the carrier 2450 a and the routing traces 2420 ofthe front substrate 2410 a. The front substrate 2410 a may be either apatterned front substrate or a preformed support front substrate whichhas insulating posts 2413 a in the display region 2401A, and stationaryelectrodes in the form of optical stacks 2414.

Referring to FIG. 24B, the carrier 2450 b is shaped to be thicker in theperipheral region 2402B than in the display region 2401B, protrudingtoward a front substrate 2410 b. The front substrate 2410 b may beeither a patterned front substrate or a preformed support frontsubstrate which has insulating posts 2413 b in the display region 2401B.Movable electrodes 2460 b are formed on the carrier 2450 b. Then, thecarrier 2450 b is laid over the front substrate 2410 b such that themovable electrodes 2460 b are interposed between the front substrate2410 b and the carrier 2450 b. Because of the thicker portion in theperiphery 2402B of the carrier 2450 b, the movable electrodes 2460 bcontact routing traces 2420 in the peripheral region 2402B of the frontsubstrate 2410 b. A skilled artisan will appreciate that various otherconfigurations of column routing structures are also possible.

III. Formation of Back Carriers

In making the interferometric modulator display device described above,movable electrodes may be formed in various ways. In many of theembodiments described herein, the movable electrodes are formed on acarrier backplate or removable carrier and then transferred to the frontsubstrate of the device.

In one embodiment, the movable electrodes are formed on a carrierbackplate, and then are transferred to the front substrate. The term“carrier backplate” refers to a plate that both serves as a carrier thattransfers a movable electrode layer for the electrostatic MEMS to afront substrate having stationary electrodes, and also forms thebackplate of the interferometric modulator display device. In otherembodiments, a removable carrier may be used only as a carrier toprovide the movable electrodes to the front substrate. The term“removable carrier” refers to a temporary or sacrificial substrate whichis removed after transferring the movable electrodes onto the frontsubstrate. When a removable carrier is used, after removal of thecarrier, a permanent backplate is further provided to seal theinterferometric modulator display device. In the embodiments describedabove, the movable electrodes may be formed by patterning a movableelectrode material on the carrier backplate or removable carrier, usingany suitable technique, e.g., photolithography and etching, or screenprinting.

In other embodiments, the carrier may be shaped to have a preformedpattern corresponding to that of the movable electrodes beforedepositing a movable electrode material thereon. Preformed patterns maybe provided by, e.g., embossing, inscribing, or depositing/etching railsand/or posts such that the movable electrode layers can bediscontinuously deposited thereon. This technique permits movableelectrode formation without additionally patterning and etching themovable electrode material after deposition. In the context of thisdocument, the carrier backplate and removable carrier with the preformedpattern are referred to as a “shaped carrier backplate” and a “shapedremovable carrier,” respectively. The shaped carrier backplate and theshaped removable carrier may be collectively referred to as “shapedcarriers.”

1. Shaped Carriers

FIG. 25 is a schematic perspective view of a shaped carrier 2500. Theshaped carrier 2500 may be either a permanent carrier backplate or aremovable carrier. As shown in FIG. 25, the shaped carrier 2500 haselongated recesses 2501 extending substantially parallel to one another.The depth of the recesses depends in part upon the thickness of materialto be deposited and the conformality of the deposition technique. In oneembodiment, the depth of the recesses is at least 3 times the thicknessof the material to be deposited. Desirably, layers to be deposited(e.g., movable electrode layers) are discontinuous due to the depth ofthe recesses. In one embodiment, the elongated recesses 2501 may have adepth from about 2,000 Å to about 12,000 Å, and particularly from about3,000 Å to about 6,000 Å. The recesses 2501 define elongated mesas 2502alternating with the recesses 2501. The shaped carrier 2500 alsoincludes movable electrodes 2510 formed on the mesas 2502. The shapedcarrier 2500 further includes excess movable electrode material 2520 inthe elongated recesses 2501. As will be better understood fromdescription below, the shaped carrier will be laid over a frontsubstrate such that the movable electrodes 2510 face the frontsubstrate.

FIGS. 26A-26D are cross sections illustrating a method of making ashaped carrier according to one embodiment. The illustrated method usesembossing for shaping the carrier. In the illustrated embodiment, asubstantially flat substrate 2600 is provided, as shown in FIG. 26A. Inan embodiment in which the carrier is a permanent backplate, thesubstrate 2600 may be formed of a metal (e.g., stainless steel), glass,or a polymeric material (e.g., polyethylene terephthalate, polyethylene,polycarbonate, and polymethyl methacrylate). In certain embodiments, thecarrier backplate may have two sublayers including a metallic sublayerand a polymeric sublayer laminated to each other. In other embodimentsin which the carrier is a removable carrier, the substrate 2600 may beformed of a polymeric material. Examples of the polymeric material willbe described below.

Then, as shown in FIG. 26B, the substrate 2600 is placed on a platen2650. The illustrated platen 2650 may be formed of a metallic material.The substrate 2600 may be heated such that the substrate 2600 is softenough to impress at a subsequent embossing step. The substrate 2600 maybe heated to a temperature which varies depending on the material usedfor the substrate 2600.

Then, an embossing plate 2651 is pressed onto the substrate 2600, asshown in FIG. 26C. The embossing plate 2651 has recesses and protrusionsshaped to produce elongated recesses 2601 (FIG. 26D) on the substrate2600. The embossing plate 2651 may be formed of a metallic material. Atleast one of the platen 2650 and the embossing plate 2651 may be in aform of a rotating cylinder. A skilled artisan will appreciate thatvarious other configurations of embossing techniques may also be adaptedfor embossing the substrate.

Then, the embossing plate 2651 is removed from the substrate 2600.

Subsequently, the substrate 2600 is removed from the platen 2650. Theresulting carrier 2600 with the elongated recesses 2601 is shown in FIG.26D. In another embodiment, the substrate may be patterned usingphotolithography and etching. In yet another embodiment, the substratemay be patterned by first inscribing predetermined portions and thenselectively etching the portions. Inscribing may be conducted usingvarious techniques, e.g., machining or laser-inscribing. It will beappreciated that various other techniques may also be used for shapingcarriers.

Subsequently, a movable electrode material is deposited on the topsurface of the shaped carrier 2600 and into the elongated recesses 2601.The deposited movable electrode material 2610, 2620 is discontinuousbetween the recesses 2601 and mesas 2602 defined by the recesses 2601.The configuration of the movable electrodes 2610 may be as describedabove with respect to the movable electrodes of FIG. 25.

a. Shaped Carrier Backplate

FIG. 27A is a schematic perspective view of a shaped carrier backplate2700 according to one embodiment. The illustrated shaped carrierbackplate 2700 includes elongated recesses 2701, edge rails 2702, railtrenches 2703, and posts 2704. The edge rails 2702 may include lateraletch holes 2705 which represent gaps in the rails. The etch holes 2705are configured to permit fluid communication between the rail trenches2703 and the elongated recesses 2701. The shaped carrier backplate 2700also includes movable electrodes 2710 supported on the edge rails 2702and the posts 2704. In certain embodiments, the posts 2704 may beomitted.

The elongated recesses 2701, the edge rails 2702, the rail trenches2703, the posts 2704, and the etch holes 2705 may be formed by embossingthe carrier backplate 2700 as described above with reference to FIGS.26A-26E. The backplate 2700 may be formed of any material suitable forembossing. Examples of such a material include, but are not limited to,glass and metal (e.g., stainless). In other embodiments, the backplate2700 may be shaped or preformed using photolithography and etching, orinscribing. A skilled artisan will appreciate that various other methodsmay be used for shaping the backplate 2700.

Referring to FIG. 27B, two of the edge rails 2702 define a correspondingone of the rail trenches 2703 therebetween while supporting the samemovable electrode 2710. In addition, two of the neighboring edge rails2702 define a corresponding one of the elongated recesses 2701therebetween while each supporting one of two neighboring movableelectrodes 2710. The rails trenches 2703 are vacant as will be betterunderstood from description below. The shaped carrier backplate 2700 mayalso have excess movable electrode material 2720 in the elongatedrecesses 2701.

Referring still to FIG. 27B, the posts 2704 extend upwards from thebottom of the rail trenches 2703. Referring also to FIG. 27D, twocolumns of posts 2704 are arranged in a direction parallel to theelongated recesses 2701. It will be appreciated that various otherarrangements of the posts are also possible. The posts 2704 havesubstantially the same height as the edge rails 2702 so that they cansupport the movable electrodes 2710.

FIG. 27C is a cross section of the shaped carrier backplate 2700 of FIG.27A, taken along lines 27C-27C. The illustrated cross section of theshaped carrier backplate 2700 shows the etch holes 2705 in the edgerails 2702. The etch holes 2705 are configured to permit fluidcommunication between the rail trenches 2703 and the elongated recesses2701. The etch holes 2705 allow an etchant to contact sacrificialmaterial in the rail trenches 2703 so that the sacrificial material canbe removed from the rail trenches 2703 during a manufacturing step, aswill be better understood from description below. The etch holes 2705have a bottom surface 2706 lower than those of the elongated recesses2701. The lower bottom surface 2706 of the edge holes 2705 prevents theexcess movable electrode material 2720 from blocking the etch holes2705. A top plan view of the shaped carrier backplate 2700 without themovable electrodes 2710 is shown in FIG. 27D.

Referring still to FIG. 27C, the carrier backplate 2700 can have threedifferent levels BL1, BL2, and BL3. The bottoms of the elongatedrecesses 2701 and the rail trenches 2703 are at a first level BL1. Thetops of the edge rails 2702 and the posts 2704 are at a second level BL2which is higher than the first level BL1. The bottom surface 2706 of theetch holes 2705 is at a third level BL3 which is lower than the firstlevel BL1. A height difference between the first and second levels BL1,BL2 allows the movable electrode material to be discontinuous betweentwo of the edge rails 2702 so as to define the movable electrodes 2710in strips. A height difference between the first and third levels BL1,BL3 prevents the excess movable electrode material 2720 from blockingthe etch holes 2705.

FIG. 28 is a schematic perspective view of a shaped carrier backplateaccording to another embodiment. The illustrated shaped carrierbackplate 2800 includes elongated recesses 2801, edge rails 2802, railtrenches 2803, and posts 2804. Unlike the shaped carrier backplate 2700of FIG. 27A, the edge rails 2802 do not include etch holes configured topermit fluid communication between the rail trenches and the elongatedrecesses. The shaped carrier backplate 2800 also includes movableelectrode 2810 supported on the edge rails 2802 and the posts 2804, andexcess movable electrode material 2820 in the elongated recesses 2801.The movable electrodes 2810 include through-holes 2811 configured topermit fluid communication between regions above and below the movableelectrodes 2810. The through-holes 2811 allow an etchant to contact asacrificial material in the rail trenches 2803 so that the sacrificialmaterial can be removed from the rail trenches 2803 during amanufacturing step, as will be better understood from description below.The through-holes 2811 may be formed using any suitable technique, forexample, photolithography and etching.

FIGS. 29A-29D illustrate one embodiment of a method of forming movableelectrodes on a shaped carrier backplate. In FIG. 29A, a shaped carrierbackplate 2900 is provided. Similar to the shaped carrier backplates2700, 2800 of FIGS. 27A and 28, the illustrated shaped carrier backplate2900 includes elongated recesses 2901, edge rails 2902, rail trenches2903, and posts 2904. In one embodiment, the shaped carrier backplate2900 have etch holes (not shown) for lateral gas transmission throughthe rails 2902, similar to the etch holes 2705 of the backplate 2700 ofFIG. 27A. In other embodiments, the shaped carrier backplate 2900 mayhave through-holes 2811 of FIG. 28.

Then, a sacrificial material 2908 is blanket-deposited over the shapedcarrier backplate 2900, overfilling the elongated recesses 2701 and therail trenches 2903, as shown in FIG. 29B. In one embodiment, thesacrificial material 2908 may be a photoresist or a polymeric materialsuch as polyimide. In another embodiment, the sacrificial material 2908may be a metallic material such as molybdenum, silicon (non-metallic),tungsten, or titanium, which is selectively etchable by a fluorine-basedetchant, particularly, XeF₂. This step may be carried out using anysuitable process, for example, a spin coating (spin-on) or sputteringprocess. In one embodiment, a metallic sacrificial material may beformed conformally on the backplate 2900. In other embodiments, aphotoresist or polymeric sacrificial material may be planar as depositedon the backplate 2900.

The sacrificial material 2908 is removed such that the sacrificialmaterial 2908 does not protrude beyond the top points of the edge rails2902 and the posts 2904. This step may be carried out using any suitableprocess, e.g., chemical mechanical polishing (CMP). This step providesmesas 2909 having a substantially flat top surface and alternating withthe elongated recesses 2901, as shown in FIG. 29C. Subsequently,portions of the sacrificial material 2908 are removed from the elongatedrecesses 2901 using any suitable process, for example, photolithographyand etching. In certain embodiments, the elongated recesses 2901 may bedeeper than the rail trenches 2903. In such embodiments, the portions ofthe sacrificial material 2908 within the elongated recesses 2901 may bemaintained therein without being removed, thus avoiding a mask step.

Next, a movable electrode material is deposited on the shaped carrierbackplate 2900, as shown in FIG. 29D. The movable electrode materialforms movable electrodes 2910 in strips which extend parallel to oneanother on the mesas 2909. In addition, an excess movable electrodematerial 2920 remains in the elongated recesses 2901.

In certain embodiments, a bonding agent is deposited on the movableelectrodes 2910 in selected locations where it is to make physical andelectrical contact to other elements in a mounting or laminationprocess. Selective application to desired locations can be achieved bydeposition, patterning, and etching, or by sputtering or PVD through ashadow mask. Particularly, the bonding agent may be applied to portions(e.g., contact pads) of the movable electrodes 2910 which will contactcolumn routing traces formed on a front substrate. In another example, acolumn driver can be directly mounted on the carrier backplate. In thefinal device structure, the portions of the movable electrodes 2910 mayoppose portions of the front substrate from which an insulating materialhas been removed or shielded so as to expose an underlying conductivelayer or trace, as described above with respect to FIGS. 20 and 21.

The bonding agent facilitates adhesion between the movable electrodesand the routing traces. The bonding agent may be formed of a conductiveadhesive material. The adhesive material may be a cold-weld materialwhich may be weldable at a relatively low temperature. Examples of thematerial include, but are not limited to, antimony (Sb), indium (In), ortin (Sn). The material may be soft and deformable. In some embodiments,the bonding agent can serve as a gap-filler 1717 as described above withrespect to FIG. 17A-17C. The bonding agent described herein may apply toany of embodiments described below with respect to carrier backplates orremovable carriers.

Although not shown, the shaped carrier backplate 2900 is then attachedto a front substrate such that the movable electrodes 2910 areinterposed between the shaped carrier backplate 2900 and the frontsubstrate. Subsequently, the sacrificial material 2908 is removed fromthe rail trenches 2903. In certain embodiments, the sacrificial material2908 may be removed prior to attaching the carrier backplate 2900 to thefront substrate. In one embodiment in which the backplate 2900 includesetch holes in the edge rails 2902 similar to those of FIG. 27A, thesacrificial material 2908 may be removed through the etch holes. Inanother embodiment in which the backplate does not have etch holes, themovable electrodes may be patterned to have through-holes similar to thethrough-holes 2811 of FIG. 28. Then, the sacrificial material 2908 maybe removed through the through-holes.

FIGS. 30A-30D illustrate another embodiment of a method of formingmovable electrodes on a shaped carrier backplate. In FIG. 29A, a shapedcarrier backplate 3000 is provided. Similar to the shaped carrierbackplates 2700, 2800 of FIGS. 27A and 28, the illustrated shapedcarrier backplate 3000 includes elongated recesses 3001, edge rails3002, rail trenches 3003, and posts 3004. In one embodiment, the shapedcarrier backplate 3000 has etch holes (not shown) in the rails 3002,similar to those of the backplate 2700 of FIG. 27A. In otherembodiments, the shaped carrier backplate 3000 may not have etch holes.

Next, seed layers 3007 are selectively deposited on portions of thebackplate 3000 on which a sacrificial material is to be deposited. Suchportions may include at least the bottom surfaces of the rail trenches3003. The seed layers 3007 can be selectively deposited through a shadowmask (not shown). Then, the seed layers 3007 are electrically connectedto a voltage source for electroplating, as shown in FIG. 30B. Forelectroplating, the backplate 3000 may be immersed in a solutioncontaining the sacrificial material. The sacrificial material may be ametallic material suitable for electroplating, for example, tungsten,molybdenum, or titanium, which is etchable by a fluorine-based etchant,particularly, XeF₂. Then, an electric potential is applied between theseed layers and an electrode also immersed in the solution. Theresulting backplate 3000 with the selectively plated sacrificialmaterial 3008 is shown in FIG. 30C. In certain embodiments, anoverburden or excess sacrificial material may be removed using anysuitable process, for example, chemical mechanical polishing (CMP), toleave the planarized structure of FIG. 30C.

Next, a movable electrode material is deposited over the shaped carrierbackplate 3000. The movable electrode material forms movable electrodes3010 in strips which extend parallel to one another. In addition, anexcess movable electrode material 3020 remains in the elongated recesses3001. After laminating the backplate 3000 with a front substrate, thesacrificial material 3008 is removed from the rail trenches 3003. Incertain embodiments, the sacrificial material 3008 may be removed priorto attaching the carrier backplate 3000 to the front substrate. Thedetails of this step may be as described above with respect to thesacrificial material removal step (FIG. 29D).

FIGS. 31A-31D illustrate yet another embodiment of a method of formingmovable electrodes on a shaped carrier backplate. In FIG. 31A, a shapedcarrier backplate 3100 is provided. Similar to the shaped carrierbackplates 2700, 2800 of FIGS. 27A and 28, the illustrated shapedcarrier backplate 3100 includes elongated recesses 3101, edge rails3102, rail trenches 3103, and posts 3104. In one embodiment, the shapedcarrier backplate 3100 has etch holes (not shown) in the rails 3102similar to those of the backplate 2700 of FIG. 27A. In otherembodiments, the shaped carrier backplate 3100 may not have etch holes.The shaped carrier backplate 3100 is provided with blocking masks 3107over the elongated recesses 3101. In one embodiment, the blocking masks3107 may be formed by screen printing or shadow masking.

Then, a sacrificial material 3108 is blanket-deposited over the shapedcarrier backplate 3100, overfilling the rail trenches 3103, as shown inFIG. 31B. The blocking masks 3107 prevent the sacrificial material 3108from being deposited in the elongated recesses 3101. The details of thisstep may be as described above with reference to FIG. 29B.

Subsequently, an excess or overburden sacrificial material 3108 isremoved such that the sacrificial material 3108 does not protrude beyondthe top points of the edge rails 3102 and the posts 3104. This step maybe carried out using any suitable planarization process, e.g., chemicalmechanical polishing (CMP). Then, the blocking masks 3107 are removedfrom the elongated recesses 3101 by, for example, an ashing process, asshown in FIG. 31C. In other embodiments, the blocking masks 3170 may beselectively removed using any suitable technique, for example, maskingand etching.

Next, a movable electrode material is deposited over the shaped carrierbackplate 3100. The movable electrode material forms movable electrodes3110 in a strip form which extend parallel to one another. In addition,an excess movable electrode material 3120 remains in the elongatedrecesses 3101. After laminating the backplate 3010 with a frontsubstrate, the sacrificial material 3108 is removed from the railtrenches 3103. The details of this step may be as described above withrespect to the sacrificial material removal step (FIG. 29D).

FIG. 32A illustrates yet another embodiment of a shaped carrierbackplate. The illustrated shaped carrier backplate 3200 has elongatedrecesses 3201 extending substantially parallel to one another. Therecesses 3201 define elongated mesas 3202 alternating with the recesses3201.

Referring to FIG. 32B, a sacrificial material 3207 b may be depositedacross the backplate 3200 so as to be discontinuous between theelongated recesses 3201 and the mesas 3202. Subsequently, a movableelectrode material is deposited across the backplate 3200, formingmovable electrodes 3210 on the mesas 3202 and excess mechanical layers3220 in the elongated recesses 3201, as shown in FIG. 32B. The movableelectrodes 3210 on the mesas 3202 and the excess mechanical layers 3220in the recesses 3201 are discontinuous with one another. In oneembodiment, the overall thickness of the movable electrode material 3220and the sacrificial material 3207 b is equal to or less than a half ofthe depth of the elongated recesses 3201. This configuration provideselectrical isolation between the movable electrodes 3210.

As will be better understood from description below, the sacrificialmaterial 3207 a on the mesas 3202 will be removed after attaching thebackplate 3200 to a front substrate (not shown). This sacrificialmaterial removal step will release the movable electrodes 3210 from thebackplate 3200 onto the front substrate. However, the sacrificialmaterial 3207 b in the elongated recesses 3201, if sealed from releaseetch, will still remain after the sacrificial material removal step. Thesacrificial material 3207 b in the elongated recesses 3201 will hold theexcess mechanical layers 3220 in place in the completed interferometricmodulator display device.

FIG. 32C illustrates a cross section of another embodiment of a methodof forming movable electrodes on a shaped removable carrier. Referringto FIG. 32C, a release layer 3207 may be deposited conformally acrossthe backplate 3200 so as to be continuous between the elongated recesses3201 and the mesas 3202. Subsequently, a movable electrode material isdeposited across the backplate 3200, forming movable electrodes 3210 onthe mesas 3202 and excess mechanical layers 3220 in the elongatedrecesses 3201. The movable electrodes 3210 on the mesas 3202 and theexcess mechanical layers 3220 are discontinuous with one another. Thisconfiguration provides electrical isolation between the movableelectrodes 3210.

As will be better understood from description below, the release layer3207 will be removed after attaching the backplate 3200 to a frontsubstrate (not shown). This removal step will release the movableelectrodes 3210 from the backplate 3200 onto the front substrate. Theexcess mechanical layers 3220 will be supported by excess mechanicallayer supports extending from the front substrate, as will be betterunderstood from description below of FIGS. 34A-34D.

FIG. 32D is a top plan view of the shaped carrier backplate 3200 of FIG.32B. FIG. 32E is a cross section of an edge portion 3250 of the shapedcarrier backplate 3200 of FIG. 32D. The edge portion 3250 includesperimeter ridges 3251 extending along the edge of the backplate 3200.The perimeter ridges 3251 define recesses 3252 therebetween. A skilledartisan will appreciate that the number of the recesses 3252 can varydepending on the design of the carrier backplate.

In one embodiment, the perimeter ridges 3251 are taller than rails 3202,and may be covered by a shadow mask during deposition of a sacrificialmaterial or mechanical layer. Thus, the edge portion 3250 may notinclude either a sacrificial material or an excess mechanical layer,while being configured to be attached to the front substrate with anintervening sealant such as frit or metal for hermetic seal. Theperimeter ridges 3251 surround the display region of the resultinginterferometric modulator display device to make a series of rings atthe substrate level L2. The perimeter ridges 3251 seal the excessmechanical layer at level L1. In other embodiments, the edge portion3250 may include a mechanical layer which can partly serve as a sealant.The perimeter ridges 3251 serve to prevent the sacrificial material 3207b in an elongated recess 3201 neighboring the edge portion 3250 frombeing removed during the sacrificial material removal step. Thisconfiguration allows the sacrificial material 3207 b in the elongatedrecess 3201 to hold the excess mechanical layer 3220 in place in thecompleted display device.

In certain embodiments, the carrier backplate 3200 may have asacrificial material blanket-deposited on the surfaces thereof,including the sidewalls of the perimeter ridges 3251. In suchembodiments, the recesses 3252 may be filled with a sealant such thatthe sacrificial material is not etched during a sacrificial layerremoval step.

FIGS. 33A-33D are cross sections illustrating a method of making ashaped carrier backplate having patterned movable electrodes accordingto another embodiment. In the illustrated embodiment, a carrierbackplate 3300 is shaped to have a plurality of posts or connectors3350, as shown in FIG. 33A. The posts 3350 may be shaped using anysuitable process such as embossing, inscribing, or photolithography andetching, the last of which provides preformed posts. Embossing orinscribing forms the posts 3350 integrally with and of the same materialas the backplate 3300.

Subsequently, a sacrificial material 3310 is deposited over thebackplate 3300. Then, the sacrificial material 3310 is etched back toexpose the posts 3350, as shown in FIG. 33B. The sacrificial material3310 may be planarized using any suitable technique, including but notlimited to, chemical mechanical polishing (CMP).

Next, a movable electrode material 3320 is deposited across thebackplate 3300, as shown in FIG. 33C. Then, the movable electrodematerial 3320 is patterned using any suitable technique, for example,photolithography and etching. The resulting movable electrodes 3320 areshown in FIG. 33D. The movable electrodes 3320 are supported on theposts 3350 and also partially on the sacrificial material 3310. In oneembodiment, the movable electrodes 3320 may be patterned to separate theelectrodes 3320 and provide release holes as described above withrespect to FIG. 28 to facilitate removing the underlying sacrificialmaterial at a removal step described below. In certain embodiments, abonding agent may be deposited on the movable electrodes 3320 inselected locations before or after patterning the movable electrodes3320. Details of the bonding agent is described above with respect toFIGS. 29A-29D.

Next, the carrier backplate 3300 is attached to a front substrate (notshown) so that the movable electrodes 3320 are interposed therebetween.Then, the sacrificial material 3310 is removed. In certain embodiments,the sacrificial material 3310 may be removed prior to attaching thecarrier backplate 3300 to the front substrate. The movable electrodes3320 are supported by rails and posts of the front substrate.

FIG. 34A is a schematic perspective view of a partially fabricatedinterferometric modulator display device 3400 according to oneembodiment. The illustrated portion of the device is a display region ofthe device 3400. The device 3400 includes a shaped front substrate 3410and a shaped carrier backplate 3450 attached to each other with movableelectrodes 3461 a interposed therebetween.

The shaped front substrate 3410 includes rails 3411 extending parallelto one another, troughs 3412 defined by the rails 3411, and opticalstacks 3414 on the bottom of the troughs 3412 and on top of the rails3411. The shaped front substrate 3410 further includes excess mechanicallayer supports 3420 formed on the rails 3411. The configurations of therails 3411, the troughs 3412, and the optical stacks 3414 may be asdescribed above with respect to those of FIG. 10.

The shaped carrier backplate 3450 includes elongated recesses 3451 andmesas 3452 defined by the elongated recesses 3451. The shaped carrierbackplate 3450 also includes excess mechanical layers 3461 b andsacrificial layers 3462 in the elongated recesses 3451. The sacrificiallayers 3462 are enclosed by the excess mechanical layers 3461 b, theelongated recesses 3451, rings of perimeter ridges (not shown) asdiscussed with respect to FIGS. 32D and 32E. The configurations of theelongated recesses 3451, the mesas 3452, the excess mechanical layers3461 b, and the sacrificial layers 3462 may be as described above withrespect to those of FIG. 32B.

The movable electrodes 3461 a are interposed between the mesas 3452 ofthe backplate 3450 and the optical stack 3414 on top of the rails 3411of the front substrate 3410. As described above with reference to FIG.32B, a sacrificial material which had been interposed between themovable electrodes 3461 a and the mesas 3452 has now been removed,releasing the movable electrodes 3461 a from the backplate 3450.Referring to FIG. 34B, the movable electrodes 3461 a are now supportedon the optical stack 3414 on top of the rails 3411 while spaced from themesas 3452 due to the removed sacrificial layer.

In the illustrated embodiment, the shaped front substrate 3410 furtherincludes excess mechanical layer supports 3420. Referring to FIGS. 34Cand 34D, the excess mechanical layer supports 3420 protrude or extendupwards from the rails 3411. In addition, the optical stacks 3414 areformed on top of the excess mechanical layer supports 3420. The excessmechanical layer supports 3420 are configured to support the excessmechanical layers 3461 b in the elongated recesses 3451 of the backplate3450. The excess mechanical layer supports 3420, together with thesacrificial layers 3462, hold up the excess mechanical layers 3461 b tothe backplate 3450. In some embodiments (for example, the backplate ofFIG. 32C) in which the backplate 3450 does not have a sacrificialmaterial in the elongated recesses 3451, only the excess mechanicallayer supports 3420 may serve to hold up the excess mechanical layers3461 b to the backplate 3450. This can happen if the sacrificial layeris removed in the recesses at the same time as on mesas of the carrierbackplate (e.g., no rings of perimeter ridges).

b. Shaped Removable Carrier

FIG. 35A is a schematic perspective view of a shaped removable carrier3500 according to one embodiment. The illustrated shaped removablecarrier 3500 includes elongated recesses 3501 running parallel to oneanother, and elongated mesas 3502 defined by the recesses 3501. Thecarrier 3500 may carry movable electrodes 3510 formed on the mesas 3502,as shown in FIG. 35B. The carrier 3500 may also carry excess mechanicallayers 3520 in the recesses 3501, which will be removed together withthe carrier 3500 after transferring the movable electrodes 3510 to afront substrate. The recesses 3501 are deep enough to ensure that thedesired thickness of the movable electrodes 3510 deposited on thecarrier 3500 is discontinuous between the mesas 3502 and the recesses3501.

In one embodiment, the shaped removable carrier 3500 may be formed of apolymeric material. The polymeric material may be dissolved, ashed, orevaporated after transferring the movable electrodes to a frontsubstrate. In other embodiments, the removable carrier 3500 may bephysically lifted or peeled from the front substrate, while leaving themovable electrodes on the front substrate. In such embodiments, themovable electrodes may be formed directly on the removable carrier 3500without an intervening sacrificial layer.

In another embodiment, the shaped removable carrier 3500 may be arecyclable carrier. The recyclable carrier may be formed of a polymericmaterial, such as a polyimide film. An exemplary polyimide film isformed of poly(4,4′-oxydiphenylene-pyromellitimide) (KAPTON® availablefrom E.I. du Pont de Nemours and Company).

In yet another embodiment, the recyclable carrier may be formed of aporous polymeric material. Referring to FIG. 35C, in such an embodiment,before forming the movable electrodes 3510 on the carrier 3500, arelease layer 3530 is formed on the carrier 3510. Then, the movableelectrodes 3510 are formed on the release layer 3530. The release layer3530 may be as thin as a single atomic layer as long as it is acontinuous film intervening at all locations between the carrier 3500and the movable electrode layer 3510, 3520. In one embodiment, therelease layer 3530 may be formed of molybdenum.

Referring to FIG. 35D, in order to transfer the movable electrodes 3510to a front substrate 3570, a release etchant is provided through theporous carrier 3500. The release etchant is able to travel through theporous carrier 3500 to reach and remove the release layer 3530, therebyreleasing the movable electrodes 3510 from the recyclable carrier 3500.The recyclable carrier 3500 may be recycled for manufacturing otherinterferometric modulator display devices.

Referring back to FIG. 19, the shaped carriers of the embodimentsdescribed above with respect to FIGS. 25-35D may have additionalstructures to form routing traces 1917 connected to the movableelectrodes 1960. A skilled artisan will appreciate that the additionalstructures may include various configurations of trenches and mesasdepending on the configuration of the routing traces, with the higherelevation features representing locations to receive functionalconductive layers to be transferred to the substrate and lower elevationfeatures representing isolation between the functional conductivelayers. In other embodiments in which a front substrate provides routingtraces similar to those shown in FIG. 17 or 18, the shaped carrier mayonly have structures for the movable electrodes without additionalstructures for the routing traces.

2. Carriers with Patterned Movable Electrodes

In some embodiments, unlike the movable electrodes on the shapedcarriers described above, movable electrodes may be patterned on acarrier. Such a carrier may be either a permanent carrier backplate or aremovable carrier. The carrier may have a substantially planar surface.In other embodiments, the carrier may have connectors or posts tosupport movable electrodes.

a. Carrier Backplate with Patterned Movable Electrodes

FIGS. 36A-36E are cross sections illustrating a method of patterningmovable electrodes on a carrier backplate according to one embodiment.In the illustrated embodiment, a substantially planar carrier backplate3600 is provided, as shown in FIG. 36A. Then, a sacrificial material3610 is deposited on the backplate 3600. Subsequently, a movableelectrode material 3620 is deposited on the sacrificial material 3610.

Referring to FIG. 36B, a photoresist layer 3630 is formed on the movableelectrode material 3620. Then, the photoresist layer 3630 is patternedto provide a mask for use in etching the movable electrode material 3620and the sacrificial material 3610, as shown in FIG. 36C.

Subsequently, the movable electrode material 3620 and the sacrificialmaterial 3610 are etched using any suitable etchants, as shown in FIG.36D. The movable electrode material 3620 can be etched by either a wetor dry etch process. In an embodiment in which the sacrificial material3610 is molybdenum, the sacrificial material 3610 may be etched by aphosphoric/acetic/nitric acid or “PAN” etchant. Finally, the photoresistlayer 3630 is removed from the carrier backplate 3600.

As described above with respect to the shaped carrier backplate, thecarrier backplate is then attached to a front substrate (not shown)having stationary electrodes, such that the movable electrodes 3620 areinterposed therebetween. Then, the sacrificial material 3610 is removedto release the movable electrodes from the backplate 3600. The movableelectrodes 3620 are supported by rails and posts of the front substrate,while being movable toward the front substrate. The carrier backplate3600 stays as a backplate, forming part of the completed interferometricmodulator display device. The details of attaching the backplate 3600 tothe front substrate will be described below with reference to FIGS.43A-43C.

FIGS. 37A-37E are cross sections illustrating a method of patterningmovable electrodes on a carrier backplate according to anotherembodiment. In the illustrated embodiment, a substantially planarcarrier backplate 3700 is provided, as shown in FIG. 37A. Then, asacrificial material 3710 is deposited on the backplate 3700.Subsequently, a movable electrode material 3720 is deposited on thesacrificial material 3710.

Referring to FIG. 37B, a photoresist layer 3730 is formed on the movableelectrode material 3720. Then, the photoresist layer 3730 is patternedto provide a mask for use in etching the movable electrode material3720, as shown in FIG. 37C. Subsequently, the movable electrode material3720 is etched using any suitable etchant, as shown in FIG. 37D. Themovable electrode material 3720 can be etched by either a wet or dryetch process. Then, the photoresist layer 3730 is removed as shown inFIG. 37E.

Then, the carrier backplate 3700 is attached to a front substrate (notshown) having stationary electrodes, such that the movable electrodes3720 are interposed therebetween. Then, the sacrificial material 3710 isremoved to release the movable electrodes from the backplate 3700. Themovable electrodes 3720 are supported by rails and posts of the frontsubstrate. Thus, the sacrificial or release layer 3710 of thisembodiment need not be patterned. The carrier backplate 3700 stays as abackplate in the final product. The details of attaching the backplate3700 to the front substrate will be described below with reference toFIGS. 43A-43C.

FIGS. 38A-38D are cross sections illustrating a method of patterningmovable electrodes on a carrier backplate according to yet anotherembodiment. In the illustrated embodiment, a substantially planarcarrier backplate 3800 is provided, as shown in FIG. 38A. Then,connectors 3850 are formed on the carrier backplate 3800. The connectors3850 may be formed using any suitable process such as photolithographyand etching. The connectors 3850 may be formed of a polymeric materialsuch as polyimide or photoresist or an inorganic material such assilicon oxide (SiO₂). In one embodiment, the connectors 3850 may beformed using a spin-on-glass technique. In another embodiment, theconnectors 3850 may be formed by embossing the backplate. In such anembodiment, the connectors 3850 are formed integrally with and of thesame material as the backplate 3800.

Subsequently, a sacrificial material 3810 is deposited over thebackplate 3800. Then, the sacrificial material 3810 is etched back tohave a thickness the same as that of the connectors 3850, as shown inFIG. 38B. The sacrificial material 3810 may be planarized using anysuitable technique, including but not limited to, chemical mechanicalpolishing (CMP).

Next, a movable electrode material 3820 is deposited across thebackplate 3800, as shown in FIG. 38C. Then, the movable electrodematerial 3820 is patterned using any suitable technique, for example,photolithography and etching. The resulting movable electrodes 3820 areshown in FIG. 38D. The movable electrodes 3820 are supported on theconnectors 3850 and also partially on the sacrificial material 3810.

Next, the carrier backplate 3900 is attached to a front substrate (notshown) so that the movable electrodes 3820 are interposed therebetween.Then, the sacrificial material 3810 is removed. The movable electrodes3820 are supported by rails and posts of the front substrate.

Referring to FIGS. 19 and 36-38, the movable electrode material may bepatterned to have routing traces 1917 connected to the movableelectrodes 1960. A skilled artisan will appreciate that the routingtraces 1917 may be formed simultaneously with or separately frompatterning the movable electrodes 1960. In other embodiments in which afront substrate provides routing traces similar to those shown in FIGS.17 and 18, the carrier backplate may only carry the movable electrodeswithout the routing traces.

FIG. 39A illustrates a partial cross section of a carrier backplate withpatterned movable electrodes and rivets. The term “rivet” refers to astructure configured to support and stiffen the movable electrodes fromon top of the electrodes in a depression during the operation of theresulting interferometric modulator display device.

The illustrated portion of the carrier backplate 3900 includes asacrificial layer 3910, a rivet supporting structure 3920, a movableelectrode 3930, and a rivet 3940. The sacrificial layer 3910 is formedon the backplate 3900, and has a recess 3911 for partially accommodatingthe rivet supporting structure 3920, the movable electrode 3930, and therivet 3940. The rivet supporting structure 3920 is formed conformally inand around the recess 3911. The rivet supporting structure 3920 may beformed of an inorganic material such as silicon oxide. In certainembodiments, the rivet supporting structure 3920 may be omitted. Themovable electrode 3930 is formed conformally in the recess 3911, in theillustrated embodiment on the rivet supporting structure 3920 and onexposed portions of the sacrificial layer 3910. Then, the rivet 3940 isformed on the movable electrode 3930, overfilling the recess 3911.Suitable materials for use in the rivet 3940 include, but are notlimited to, aluminum, AlO_(x), silicon oxide, SiN_(x), nickel andchromium. Alternate materials which may be used to form the rivet 3940include other metals, ceramics, and polymers. The thickness of the rivet3940 will vary according to the mechanical properties of the materialused.

FIG. 39B is a cross section of an interferometric modulator displaydevice having rivets on a carrier backplate according to one embodiment.The illustrated portion of the device includes a front substrate 3950and a carrier backplate 3900. The front substrate 3950 includes rails3951, troughs 3952 defined by the rails 3951, and optical stacks 3953 onthe bottom of the troughs 3952 and on top of the rails 3951. Theconfiguration of the backplate 3900 is identical to that of thebackplate 3900 of FIG. 39A except that the sacrificial layer 3910 hasbeen removed. The backplate 3900 opposes the front substrate 3950 withthe movable electrodes 3930 interposed therebetween. The rivets 3940 areinterposed between the movable electrodes 3930 and the optical stack3953 on the rails 3951. The rivets 3940 serve to support and stiffen themovable electrodes 3930 during operation of the interferometricmodulator display device. In another embodiment, the front substrate3950 may have posts in the troughs 3952, and the backplate 3900 mayfurther include rivets opposing the posts. In yet another embodiment, aninterferometric modulator display device may have the rail/rivetstructures described above to support movable electrodes while having nopost on the front substrate 3950. A skilled artisan will appreciate thatvarious configurations of rivets can be combined with the supports ofthe front substrate.

b. Removable Carrier with Patterned Movable Electrodes

In some embodiments, a removable carrier with patterned movableelectrodes may be used instead of a permanent carrier backplate toprovide movable electrodes to a front substrate. The removable carriermay be formed of a polymeric material. The polymeric material may bedissolvable or ashable after transferring the movable electrodes to afront substrate. In other embodiments, the removable carrier may bephysically lifted or peeled from the front substrate, while leaving themovable electrodes on the front substrate. In another embodiment, theremovable carrier may be a recyclable carrier. The recyclable carriermay be formed of a porous polymeric material. In such an embodiment,before forming movable electrodes on the carrier, a release layer may beformed on the carrier similar to the release layer 3530 of FIG. 35C.Then, a movable electrode material is deposited and patterned on therelease layer. The release layer may be a single atomic layer. In oneembodiment, the release layer may be formed of molybdenum. The detailsof patterning the movable electrodes may be as described above withreference to FIGS. 36 and 37. A skilled artisan will appreciate thatvarious configurations of removable carriers can be used to carrypatterned electrodes.

Then, the removable carrier is placed on the front substrate such thatthe patterned movable electrodes are interposed therebetween.Subsequently, the removable carrier is removed, for example, asdescribed above with reference to FIG. 35D. After the removable carrieris removed, a permanent backplate, e.g., a glass plate, is furtherprovided to seal the interferometric modulator display device. In someembodiments, a desiccant is provided between the front substrate and thepermanent backplate to prevent moisture damage to the display device.

IV. Lamination

Some of the embodiments described above provide three different types offront substrates having stationary electrodes: a shaped front substrate,a patterned front substrate (characterized by support structures beingformed independently from patterning of the stationary electrodes), anda preformed support front substrate. In addition, the other embodimentsdescribed above provide four different types of carriers: a shapedcarrier backplate, a carrier backplate with patterned movableelectrodes, a shaped removable carrier, and a removable carrier withpatterned movable electrodes. One of the types of front substrates maybe combined with one of the types of the carriers to form a partiallyfabricated or complete interferometric modulator display device. Inanother embodiment, movable electrodes may be formed directly on ashaped front substrate, not being transferred from a carrier. Possiblecombinations of the front substrates and carriers are shown below inTable 1. Various embodiments based on the combinations will also bedescribed below. Each number in Table 1 indicates the heading number ofeach embodiment described below.

TABLE 1 Patterned Preformed Shaped Front Front Support Front Substratesubstrate Substrate Shaped Carrier Backplate 1 2 3 Shaped RemovableCarrier 4 5 6 Carrier Backplate with 7 8 9 Patterned Movable ElectrodesRemovable Carrier with 10 11 12 Patterned Movable Electrodes TraditionalDeposition of 13 N/A N/A Movable Electrodes and Attachment of Backplate

1. Shaped Carrier Backplate and Shaped Front Substrate A. Embodiment A

In one variant of combination 1 in Table 1 above, a shaped carrierbackplate and a shaped front substrate may be combined with each otherto form an interferometric modulator display device. The configurationof the shaped front substrate may be as described above with referenceto one or more of FIGS. 10, 11A-11B, 16A-18C, and 34A-34D. Theconfiguration of the shaped carrier backplate may be as described abovewith reference to one of FIGS. 27A-27D, 28, and 32A-33D. The combinedstructure of the front substrate and the backplate may be as describedabove with reference to one or more of FIGS. 8, 9, 13-15, 17A-18C,34A-34D. The interferometric modulator display device made by theprocess described herein may have a relatively small gap (e.g., betweenabout 6,500 Å and about 20 μm, and particularly between about 2 μm andabout 15 μm or between about 10,000 Å and about 5 μm) between the frontsubstrate and the backplate thereof.

In the embodiments described in this disclosure, a gap between a frontsubstrate and a backplate generally refers to a gap between the bottomof the deepest trough of the front substrate (e.g., the bottom F1 of thedeepest trough 1012 c in FIG. 11A) and a backplate surface facing thefront substrate when the backplate overlies the front substrate. Thebackplate surface is one which is most removed from the front substrate(e.g., an elongated recess bottom surface B1 which faces the frontsubstrate in FIG. 26D, and the bottom surface B2 of an etch hole 2705 inFIG. 27C). Thus, for example, in FIGS. 34A and 34C, the gap between thefront substrate and the backplate refers to a gap G between the bottomof the deepest trough and the ceiling surface of the elongated recess3451 of the backplate 3450 when the backplate overlies the frontsubstrate.

The display device includes movable electrodes between the frontsubstrate and the backplate. The movable electrodes may be supported onrails and posts of the front substrate as shown in FIG. 13. In oneembodiment, the movable electrodes may also be suspended from thebackplate as shown in FIG. 27A-27D, 28, or 33D. In yet anotherembodiment, excess mechanical layers on the carrier backplate may besupported by excess mechanical layer supports as shown in FIGS. 34A-34D.

In any of embodiments described below, electrical connection betweenelectrodes (column and row electrodes) and routing structures/traces canbe established using any suitable bonding technique. Such bondingtechniques may involve using, for example, a shadow masks and a bondingagent (FIGS. 17A-17C, 20, and 21), conductive beads and insulating seal,or anisotropic conductive films (ACFs) (FIGS. 16E and 16F). Variousrouting and packaging structures and methods will be described below.

a. Routing Option 1

In one embodiment, the shaped front substrate may include a columnrouting structure for routing movable (column) electrodes as describedabove with reference to FIGS. 17A-17C. The shaped carrier backplate maycarry movable electrodes, but no leads or routing traces extending fromthe movable electrodes. When the front substrate and the backplate areattached to each other, the end portions of the movable electrodes makecontact with conductive routing traces on the front substrate. Referringback to FIGS. 17A-17C, gap-fillers 1717 may be interposed between themovable electrodes 1760 and the routing traces 1714 a 2. The columnrouting structure includes routing traces on mesas defined by columnisolation trenches. The column routing structure also includesstationary electrode layers (including an ITO layer) in the trenches, asshown in FIGS. 17A-17C. Details of the column routing structure may beas described above with reference to FIGS. 17A-17C. The shaped frontsubstrate may also include a row routing structure similar to that ofFIGS. 16A-16E. In embodiments discussed below and shown in FIGS. 40-41C,routing structures may be all on a front substrate.

Referring now to FIG. 40, after the front substrate 4010 and thebackplate 4050 are attached to each other, a driver 4020 may be mountedon the front substrate 4010. The driver may be a column driver fordriving the movable (column) electrodes, a separate row driver fordriving fixed (row) electrodes, or a combination of the two.

FIGS. 41A-41C illustrate various driver arrangements for aninterferometric modulator display device. Referring to FIG. 41A, aninterferometric modulator display device 4100A includes a shaped frontsubstrate 4110 a and a shaped carrier backplate 4150 a mounted thereon.The device 4100A also includes a column driver 4130 a and a row driver4140 a together mounted on the front substrate 4110 a on the same sideof the display region 4101 a of the device 4100A. The front substrate4110 a also includes a column routing structure 4131 a and a row routingstructure 4141 a which lead to the column and row drivers 4130 a, 4140a, respectively, as shown in FIG. 41A. The configuration of the columnrouting structure 4131 a may be as described above with reference toFIGS. 17A-17C. The configuration of the row routing structure 4141 a maybe as described above with reference to FIGS. 16A-16E. In theillustrated embodiment, exposed portions of the routing structures 4131a, 4141 a may be covered with a capping material.

Referring to FIG. 41B, an interferometric modulator display device 4100Bincludes a shaped front substrate 4110 b and a shaped carrier backplate4150 b. The device 4100B also includes a column driver 4130 b and a rowdriver 4140 b on the front substrate 4110 b on two different sides ofthe display region 4101 b of the device 4100B. The front substrate 4110b also includes a column routing structure 4131 b and a row routingstructure 4141 b which lead to the column and row drivers 4130 b, 4140b, respectively, as shown in FIG. 41B. The configuration of the columnrouting structure may be as described above with reference to FIGS.17A-17C. The configuration of the row routing structure may be asdescribed above with reference to FIG. 16. In the illustratedembodiment, exposed portion of the routing structures 4131 b, 4141 b maybe covered with a capping material.

Referring to FIG. 41C, an interferometric modulator display device 4100Cincludes a shaped front substrate 4110 c and a shaped carrier backplate4150 c. The device 4100C also includes a column driver 4130 c, a firstrow driver 4140 c 1, and a second row driver 4140 c 2 on the frontsubstrate 4110 b on the same side of the display region 4101 c of thedevice 4100C. The front substrate 4110 c also includes a column routingstructure 4131 c, a first row routing structure 4141 c 1, and a secondrow routing structure 4141 c 2 which lead to the column and row drivers4130 c, 4140 c 1, 4140 c 2, respectively. In the illustrated embodiment,alternate rows can be routed from alternate sides, which creates moreroom for row routing traces. The configuration of the column routingstructure 4131 c may be as described above with reference to FIGS.17A-17A. The configurations of the row routing structures 4141 c 1, 4141c 2 may be as described above with reference to FIG. 16. In theillustrated embodiment, exposed portion of the routing structures 4131c, 4141 c 1, 4141 c 2 may be covered with a capping material.

In other embodiments, column and row drivers can be combined with eachother, forming a single integrated column/row driver. In suchembodiments, the interferometric display device may have a layoutsimilar to those shown in FIGS. 41A and 41C. It will be appreciated thatvarious other layouts are also possible.

b. Routing Option 2

In another embodiment, the shaped front substrate may include columnrouting traces for routing movable (column) electrodes as describedabove with reference to FIGS. 18A-18C. The shaped carrier backplate maycarry movable electrodes, but no leads or routing traces extending fromthe movable electrodes. In addition, a bonding agent can be applied toends of the movable electrodes so as to facilitate electrical contactand adhesion with the routing traces. When the front substrate and theshaped carrier backplate are attached to each other, the end portions ofthe movable electrodes make contact with the routing traces. Details ofthe column routing traces may be as described above with reference toFIGS. 18A-18C. The shaped front substrate may also include a row routingstructure similar to that of FIGS. 16A-16E. In addition, theinterferometric modulator display device may have various arrangementsof drivers as described above with reference to FIGS. 41A-41C.

c. Routing Option 3

In yet another embodiment, a shaped front substrate 4210 includes a rowdriver 4240 while a shaped carrier backplate 4250 includes a columndriver 4230, as shown in FIG. 42A. The shaped front substrate 4210 mayhave a row routing structure 4241 as described above with reference toFIGS. 16A-16E. The shaped carrier backplate 4250 may have column routingtraces 4231 extending from movable electrodes, similar to the routingtraces 1917 of FIG. 19. The column routing traces 4231 provideelectrical connection between the movable electrodes and the columndriver 4230.

Referring to FIGS. 42A-42C, the front substrate 4210 and the backplate4250 oppose each other only in the display region 4201 and a portion4202 a of the peripheral region 4202 surrounding the display region4201. Each of the front substrate 4210 and the backplate 4250 has adriver chip region for the row or column driver 4230, 4240. The driverchip regions are exposed to allow the drivers 4230, 4240 to be attachedthereto. In the illustrated embodiment, contact and bonding pads may notbe aligned with each other. All of the movable electrodes and columnrouting traces can be on the backplate 4250 while all of stationaryelectrodes and row routing traces can be on the front substrate 4210.These routing structures can be formed by extension of trenches (rows)or mesas (columns) to simplify the lamination process. Thisconfiguration involves no contact/bonding pad match elevation issueswhile allowing full advantages of “pattern by elevation.” A skilledartisan will appreciate that various other routing arrangements of thefront substrate and the backplate are also possible.

d. Routing Option 4

In yet another embodiment, a shaped carrier backplate may carry movableelectrodes and routing traces similar to those shown in FIG. 19. Therouting traces are configured to extend from the movable electrodes torespective contact pads. A corresponding shaped front substrate includesa contact pad area. The contact pad area of the front substrate includesleads that are configured to make contact with the contact pads of thebackplate. The contact pad area of the front substrate may also includeleads connected to stationary (row) electrodes in its display region.The contact pads on the front substrate and backplate line up when thefront substrate and backplate are attached to each other. The contactpads on the front substrate and backplate may be connected through ananisotropic conductive film (ACF).

e. Packaging and Sealing

FIGS. 43A-43C illustrate a method of packaging and sealing aninterferometric modulator display device according to one embodiment.Referring to FIG. 43A, a shaped front substrate 4310 having cavities andstationary electrodes (not shown) is provided with a sealant 4370. Thedetails of the shaped front substrate 4310 are as described above withreference to one or more of FIGS. 10, 11A-11B, 16A-18C, and 34A-34D. Thesealant 4370 is applied along the edges of the display region 4301 ofthe front substrate 4310. In certain embodiments, sealing beads can beplaced on the edges of the backplate. The sealant 4370 is formed betweenthe display region 4301 and the contact pad (or driver chip) region 4320of the front substrate 4310. The sealant 3470 may be a hermetic sealant.In one embodiment, the sealant may be an electrically conductivematerial such as lead-based solder or non-lead-based solder. In such anembodiment, routing leads or traces contacting the conductive sealantneed to be insulated. In another embodiment, the sealant may be aninsulating material such as glass frit or epoxy polymer.

Then, a shaped carrier backplate 4350 with movable electrodes 4360formed thereon is placed on the front substrate 4310 to cover thedisplay region 4301 of the front substrate 4310, as shown in FIG. 43B.The resulting interferometric modulator display device is shown in FIG.43C.

Referring back to FIGS. 17A-17C and 20, shadow masks may be used whendepositing a dielectric material on a shaped front substrate. A shadowmask may be used to establish electrical connection between variouselements of an interferometric modulator display device. For example, ashadow mask can be used to expose portions of the column routing traceson the front substrate for electrical connection between the routingtraces and movable (column) electrodes (on a backplate or removablecarrier) and between the routing traces and a column driver (see FIGS.17A-17C, and 20). A shadow mask can also be used to expose portions ofmovable electrode landing pads on a front substrate for electricalconnection between movable electrode routing traces on a backplate (seeFIG. 19) and a column driver mounted on the front substrate. A shadowmask can be used to expose portions of the row routing traces/landingpads on the front substrate for electrical connection between therouting traces and a row driver mounted on the front substrate.

The shadow mask blocking sections of interest are connected to oneanother as shown in FIG. 44A. The shadow masks 4420 include first,second, and third blocking portions 4420 a, 4420 b, 4420 c to cover arow driver chip region, portions of the column routing traces, and acolumn driver chip region, respectively. The second blocking portion4420 b for blocking portions of the routing traces may be connected tothe third blocking portion 4420 c for blocking the column driver chipregion via shadow mask connectors 4421. With the blocking portions 4420a, 4420 b, 4420 c between the front substrate 4410 and a sputteringtarget, a dielectric material is deposited across the front substrate4410. In other embodiments, CVD or evaporating methods can also be usedfor forming the dielectric material on the front substrate 4410. As aresult, portions covered by the shadow mask 4420 are substantially freeof the dielectric material, exposing an underlying conductive layer.This configuration provides bonding regions for electrical connection,e.g., contacts between movable electrodes and column routing traces(4420 b), and landing pads for a column driver (4420 c) and a row driver(4420 a). The dielectric material is deposited on other portions notcovered by the shadow mask 4420, forming part of an optical stack. Thedielectric layer serves to passify conductors in routing regions.Similarly, portions of the conductive layer under the connectors 4421are also exposed because the connectors 4421 mask the portions duringthe dielectric material deposition.

After depositing the dielectric material, a sealant may be applied tothe edges of the display region 4401. In the illustrated embodiment, thesealant is formed along a sealing region 4470 surrounding the displayregion 4401. The sealing region 4470 has an annular shape, and has afirst width W1 extending in a direction toward the array region 4401.The sealant may contact the portions of conductive layers undesirablyexposed through the dielectric layer because of the connectors 4421. Inan embodiment in which the sealant is formed of a conductive material,there may be an electrical connection between the conductive layer andthe sealant, which may cause an electrical current to flow through thesealant, and shorting the exposed conductors. This may cause malfunctionof the interferometric modulator display device.

In order to prevent such an electrical short, the shaped front substrate4410 may be provided with at least one isolation trench or recess 4430at an intersection between the shadow mask connector 4421 and thesealing region 4470. The trench 4430 has a second width W2 extending inthe direction toward the array region 4401. The second width W2 of thetrench 4430 may be greater than the first width W1 of the sealing region4470 such that trench 4430 extends across a portion of the sealingregion 4470. The trench 4430 has a depth sufficient to make theconductive layer discontinuous between the bottom of the trench 4430 andthe surface of the front substrate 4410, and its position and widthensures the connector 4421 is narrower than the trench 4430 in theregion of overlap, as shown in FIG. 44C.

FIGS. 44B-44E illustrate a method of forming a sealant on the frontsubstrate 4410 having the isolation trench 4430 according to oneembodiment. First, a conductive layer 4402 a, 4402 b is formed on thefront substrate 4410 and the bottom of the isolation trench 4430, asshown in FIG. 44C. Then, the shadow masks 4420 are placed over the frontsubstrate 4410 such that the connector 4421 covers a portion of theisolation trench 4430 while exposing two side edges 4430 a, 4430 b ofthe trench 4430 as shown in FIGS. 44B and 44C. Subsequently, adielectric material 4403 is deposited on the front substrate 4410 whilecoating the side edges 4430 a, 4430 b of the trench 4430, as shown inFIG. 44D. Subsequently, the shadow masks 4420 are removed from the frontsubstrate 4410. Next, a sealant 4471 is formed on the sealing region4470 (FIG. 44A) and into the trench 4430, as shown in FIG. 44E. Thesealant 4471 contacts the isolated conductive material 4402 a on thebottom of the trench 4430. However, the dielectric material 4403 on theside edges 4430 a, 4430 b of the trench 4430 prevents the sealant 4471from being electrically connected to the conductive layer 4402 b on thetop surface of the front substrate 4410. This configuration thusprevents an electrical short between the sealant 4471 and the conductivelayer 4402 b.

In another embodiment in which an insulating sealant is used, the frontsubstrate does not have an isolation trench. In certain embodiments inwhich the shaped back substrate has routing traces exposed to theoutside as in the routing option 3 described above with respect to FIGS.42A-42C, an insulating material may be deposited and patterned on therouting traces to prevent an electrical short between the routing tracesand a conductive sealant because only contact pads needed are for thedrivers outside the seal.

B. Embodiment B

In another variant on combination 1 of Table 1 above, a shaped frontsubstrate may be combined with a shaped carrier backplate having no edgerails and posts to form an interferometric modulator display device. Theconfiguration of the shaped front substrate may be as described abovewith reference to one or more of FIGS. 10, 11A-11B, 16A-18C, and34A-34D. The configuration of the shaped carrier backplate may be asdescribed above with respect to the shaped carrier of FIG. 32B or 32C.The combined structure of the front substrate and the backplate may beas described above with reference to one or more of FIGS. 8, 9, 13-15,17A-18C, 34A-34D. The routing and packaging structures described abovemay also apply to this embodiment.

In the embodiments described above in which a shaped front substrate anda shaped carrier backplate are used to form an interferometric modulatordisplay device, a partial wetting black mask which is described belowwith respect to FIGS. 53A-53D may be used. In some embodiments, apatterned black mask which is also described below may be used.

2. Shaped Carrier Backplate and Patterned Front Substrate

In another embodiment, combination 2 of Table 1 above, a shaped carrierbackplate and a patterned front substrate may be combined with eachother to form an interferometric modulator display device. Theconfiguration of the patterned front substrate may be as described abovewith reference to FIG. 22C. The configuration of the shaped carrierbackplate may be as described above with reference to one of FIGS.27A-27C, 28, and 32A-33D. The interferometric modulator display devicemade by the process described herein may have a relatively small gap(e.g., between about 6,500 Å and about 20 μm, and particularly betweenabout 2 μm and about 15 μm or between about 10,000 Å and about 5 μm)between the front substrate and the backplate thereof.

In one embodiment, the patterned front substrate may have conductiveposts for routing movable electrodes, as shown in FIG. 22C. In otherembodiments, the shaped carrier backplate may have a routing structureas shown in FIG. 24A or 24B. In the embodiments described above, apatterned black mask may be used to avoid unwanted reflections in thepost area.

3. Shaped Carrier Backplate and Preformed Support Front Substrate

In yet another embodiment, combination 3 of Table 1 above, a shapedcarrier backplate and a preformed support front substrate may becombined with each other to form an interferometric modulator displaydevice. The configuration of the preformed support front substrate maybe as described above with reference to FIG. 23C, and is structurallysimilar to a shaped front substrate, except that the support structures(e.g., posts and rails) are not integral with the substrate and can beformed of a different material to allow separate selection of materialsfor different functions. The configuration of the shaped carrierbackplate may be as described above with reference to one of FIGS. 27,28, and 32. The interferometric modulator display device made by theprocess described herein may have a relatively small gap (e.g., betweenabout 6,500 Å and about 20 μm, and particularly between about 2 μm andabout 15 μm or between about 10,000 Å and about 5 μm) between the frontsubstrate and the backplate thereof.

In one embodiment, the preformed support front substrate may haveconductive posts for routing movable electrodes, as shown in FIG. 23C.In other embodiments, the shaped carrier backplate may have a routingstructure as shown in FIG. 24A or 24B. In the embodiments describedabove, a patterned black mask or partial wetting black mask (see FIGS.53A-53D and attendant description) may be used to avoid unwantedreflections in the post area.

4. Shaped Removable Carrier and Shaped Front Substrate

In yet another embodiment, combination 4 of Table 1 above, a shapedremovable carrier is used to provide movable electrodes onto a shapedfront substrate to form an interferometric modulator display device. Theconfiguration of the shaped front substrate may be as described abovewith reference to one or more of FIGS. 10, 11A-11B, 16A-18C, and34A-34D. The configuration of the shaped removable carrier 4550 may beas described above with reference to FIGS. 35A-35D.

Referring to FIG. 45A, a shaped removable carrier 4550 with movableelectrodes 4560 is placed over the shaped front substrate 4510 (detailsomitted for simplicity). The movable electrodes 4560 are interposedbetween the front substrate 4510 and the carrier 4550, as shown in FIG.45B. Then, the movable electrodes 4560 are released from the carrier4550, such as by etching a release layer (not shown) on the carrier asdescribed with respect to FIGS. 35A-35D. Simultaneously with releasingthe movable electrodes 4560 or subsequently thereafter, the carrier 4550is removed from the front substrate 4510, as shown in FIG. 45C. When thecarrier 4550 is removed, excess mechanical layers in elongated recessesof the carrier 4550 may also be removed along with the carrier 4550. Incertain embodiments, the excess mechanical layers may remain on thefront substrate 4510. In such embodiments, the front substrate 4510 mayhave excess mechanical layer supports as described with respect to FIGS.34A-34D to support the excess mechanical layers. Next, a sealant 4570 isprovided on the front substrate 4510. Finally, a permanent backplate4580 is provided over the front substrate 4510 to cover the movableelectrodes 4560 and remain in the final device. In one embodiment, thebackplate 4580 may have a recess to accommodate the movable electrodes4560 and optionally a drying agent or desiccant. The sealant 4570 may beformed of an insulating material, e.g., epoxy polymer. In anotherembodiment, the sealant 4570 may be formed of a conductive material. Thesealant 4570 may be configured to provide hermetic sealing to theinterferometric modulator display device.

In some embodiments, the shaped front substrate has a routing structureas described above with respect to the routing option 1 or 2 in whichthe carrier provides no routing traces extending from the movableelectrodes. In other embodiments, the carrier may provide fully definedcolumn routing traces similar to those shown in FIG. 19. In suchembodiments, the front substrate has no routing structure, and therouting traces are transferred onto the front substrate simultaneouslywith the movable electrodes. In the embodiments described above, apartial wetting black mask or patterned black mask (FIGS. 53A-53D) maybe used.

5. Shaped Removable Carrier and Patterned Front Substrate

In yet another embodiment, combination 5 of Table 1 above, a shapedremovable carrier is used to provide movable electrodes onto a patternedfront substrate to form an interferometric modulator display device. Theconfiguration of the patterned front substrate may be as described abovewith reference to FIG. 22C. The configuration of the shaped removablecarrier may be as described above with reference to FIGS. 35A-35C. Theinterferometric modulator display device in this embodiment may be madein a manner similar to that of the method described above with respectto the shaped removable carrier and the shaped front substrate. In thisembodiment, a black mask may be used to avoid unwanted reflection in thevicinity of the support structures.

6. Shaped Removable Carrier and Preformed Support Front Substrate

In yet another embodiment, combination 6 of Table 1 above, a shapedremovable carrier is used to provide movable electrodes onto a preformedsupport front substrate to form an interferometric modulator displaydevice. The configuration of the preformed support front substrate maybe as described above with reference to FIG. 23C and is structurallysimilar to a shaped front substrate, except that the support structures(e.g., posts and rails) are not integral with the substrate and can beformed of a different material to allow separate selection of materialsfor different functions. The configuration of the shaped removablecarrier 4550 may be as described above with reference to FIGS. 35A-35C.The interferometric modulator display device in this embodiment may bemade in a manner similar to that of the method described above withrespect to the shaped removable carrier and the shaped front substrate.In this embodiment, a patterned or partial wetting black mask (see FIG.53A-53D and attendant description) may be used.

7. Carrier Backplate with Patterned Movable Electrodes and Shaped FrontSubstrate

In another embodiment, combination 7 of Table 1 above, a carrierbackplate with patterned movable electrodes may be combined with ashaped front substrate to form an interferometric modulator displaydevice. The configuration of the shaped front substrate may be asdescribed above with reference to one or more of FIGS. 10, 11A-11B, and16A-18C. The configuration of the carrier backplate may be as describedabove with reference to one of FIG. 36E, 37E, 38D or 39A-39B. Thecombined structure of the front substrate and the backplate may be asdescribed above with reference to one or more of FIGS. 8, 9, 13-15,17A-18C, and 34A-34D. The interferometric modulator display device madeby the process described herein may have a relatively small gap (e.g.,between about 6,500 Å and about 20 μm, and particularly between about 2μm and about 15 μm or between about 10,000 Å and about 5 μm) between thefront substrate and the backplate thereof.

The movable electrodes may be supported on rails and posts of the frontsubstrate as shown in FIG. 13. In another embodiment, the movableelectrodes may be suspended from the backplate using posts or rivets, asshown in FIG. 38D or 39B. The movable electrodes may be pinned by postsor rails from both the front substrate and the backplate. Certainexamples of pinning by posts or rails will be described below withreference to FIGS. 46A-48. The routing options 1 and 2 described abovemay apply to this embodiment. In addition, the packaging and sealingstructures described above may apply to this embodiment. In theembodiments described above, a partial wetting black mask (see FIG.53A-53D and attendant description) or patterned black mask may be used.

8. Carrier Backplate with Patterned Movable Electrodes and PatternedFront Substrate

In another embodiment, combination 8 of Table 1 above, a carrierbackplate with patterned movable electrodes may be combined with apatterned front substrate to form an interferometric modulator displaydevice. The configuration of the carrier backplate may be as describedabove with reference to one of FIG. 36E, 37E, 38D or 39A-39B. Theconfiguration of the patterned front substrate may be as described abovewith reference to FIG. 22C. The interferometric modulator display devicein this embodiment may be made in a manner similar to that of the methoddescribed above with respect to the carrier backplate with patternedmovable electrodes and the shaped front substrate. The interferometricmodulator display device made by the process described herein may have arelatively small gap (e.g., between about 6,500 Å and about 20 μm, andparticularly between about 2 μm and about 15 μm or between about 10,000Å and about 5 μm) between the front substrate and the backplate thereof.In this embodiment, a patterned black mask may be used to avoid unwantedreflection in the vicinity of the support structures on the frontsubstrate.

9. Carrier Backplate with Patterned Movable Electrodes and PreformedSupport Front Substrate

In another embodiment, combination 9 of Table 1 above, a carrierbackplate with patterned movable electrodes may be combined with apreformed support front substrate to form an interferometric modulatordisplay device. The configuration of the carrier backplate may be asdescribed above with reference to one of FIG. 36E, 37E, 38D or 39A-39B.The configuration of the preformed support front substrate may be asdescribed above with reference to FIG. 23C and is structurally similarto a shaped front substrate, except that the support structures (e.g.,posts and rails) are not integral with the substrate and can be formedof a different material to allow separate selection of materials fordifferent functions. The interferometric modulator display device inthis embodiment may be made in a manner similar to that of the methoddescribed above with respect to the carrier backplate with patternedmovable electrodes and the shaped front substrate. The interferometricmodulator display device made by the process described herein may have arelatively small gap (e.g., between about 6,500 Å and about 20 μm, andparticularly between about 2 μm and about 15 μm or between about 10,000Å and about 5 μm) between the front substrate and the backplate thereof.In this embodiment, a patterned or partial wetting black mask (see FIGS.53A-53D and attendant description) may be used.

10. Removable Carrier with Patterned Movable Electrodes and Shaped FrontSubstrate

In yet another embodiment, combination 10 of Table 1 above, a removablecarrier with patterned movable electrodes is used to provide movableelectrodes onto a shaped front substrate to form an interferometricmodulator display device. The configuration of the removable carrier maybe as described immediately above the discussion of lamination. Theconfiguration of the shaped front substrate may be as described abovewith reference to one or more of FIGS. 10, 11A-11B, 16A-18C, and34A-34D. The interferometric modulator display device in this embodimentmay be made in a manner similar to that of the method described abovewith respect to the shaped removable carrier and the shaped frontsubstrate. In this embodiment, a partial wetting black mask (see FIGS.53A-53D and attendant description) or patterned black mask may be used.

11. Removable Carrier with Patterned Movable Electrodes and PatternedFront Substrate

In another embodiment, combination 11 of Table 1 above, a removablecarrier with patterned movable electrodes is used to provide movableelectrodes onto a patterned front substrate to form an interferometricmodulator display device. The configuration of the removable carrier maybe as described immediately above the discussion of lamination. Theconfiguration of the patterned front substrate may be as described abovewith reference to FIG. 22C. The interferometric modulator display devicein this embodiment may be made in a manner similar to that of the methoddescribed above with respect to the shaped removable carrier and theshaped front substrate. In this embodiment, a patterned black mask maybe used.

12. Removable Carrier with Patterned Movable Electrodes and PreformedSupport Front Substrate

In another embodiment, combination 12 of Table 1 above, a removablecarrier with patterned movable electrodes is used to provide movableelectrodes onto a preformed support front substrate to form aninterferometric modulator display device. The configuration of theremovable carrier may be as described immediately above the discussionof lamination. The configuration of the preformed support frontsubstrate may be as described above with reference to FIG. 23C and isstructurally similar to a shaped front substrate, except that thesupport structures (e.g., posts and rails) are not integral with thesubstrate and can be formed of a different material to allow separateselection of materials for different functions.

The interferometric modulator display device in this embodiment may bemade in a manner similar to that of the method described above withrespect to the shaped removable carrier and the shaped front substrate.In one embodiment, the removable carrier is attached to the frontsubstrate. Then, the patterned movable electrodes are released from theremovable carrier by removing a release layer or a sacrificial layerinterposed between the movable electrodes and the carrier. Subsequently,the carrier is removed using any suitable method, e.g., lifting,peeling, ashing, etc., while leaving the movable electrodes on the frontsubstrate. Then, a permanent backplate is provided to cover the arrayregion of the front substrate. The movable electrodes can be supportedby various support structures on the front substrate and/or thepermanent backplate (see FIGS. 46A-51). In this embodiment, a patternedor partial wetting black mask (see FIGS. 53A-53D and attendantdescription) may be used.

13. Shaped Front Substrate and Traditional Deposition of MovableElectrodes

In yet another embodiment, combination 13 of Table 1 above, a shapedfront substrate having rails and troughs in its display region isprovided. Then, a sacrificial material is provided to overfill thetroughs of the front substrate. The sacrificial material is thenplanarized to provide a substantially flat surface together with theexposed rails of the front substrate. Subsequently, a movable electrodematerial is deposited and patterned on the front substrate to definemovable electrodes, using any suitable process, e.g., photolithographyand etching. Then, a permanent backplate is placed over the frontsubstrate as described above with respect to the shaped removablecarrier and the shaped front substrate. The movable electrodes can besupported by various support structures on the front substrate and/orthe permanent backplate (see FIGS. 46A-51). In this embodiment, apartial wetting black mask (see FIGS. 53A-53D and attendant description)or patterned black mask may be used.

V. Spacers for Maintaining Space between Front Substrate and Backplate

In one embodiment, an interferometric modulator display device isprovided with spacers to maintain a space between the front substrateand the backplate thereof. Particularly, the spacers are positioned inthe display region of the interferometric modulator display device tomaintain a substantially uniform space in the display region. Thespacers serve to reduce pressure-related variability across the array ofthe display device, which can strongly affect the position of themovable electrodes across the array differently. Greater uniformityallows for larger display sizes without loss of yield. In embodimentsdescribed below, the front substrate may be a shaped, patterned, orpreformed support front substrate. The backplate may be a shaped carrierbackplate, a carrier backplate with patterned movable electrodes, or apermanent backplate provided after using a removable carrier. Moreover,the techniques and structures provided herein allow provision of a gapsubstantially smaller than traditionally assembled front substrates andbackplates.

Referring to FIGS. 46A and 46B, an interferometric modulator displaydevice 4600 includes a front substrate 4610 and a backplate 4650. Thefront substrate 4610 includes rails (not shown) defining troughs 4612.The front substrate 4610 also includes support structures in the form ofposts 4613 in the troughs 4612. The device 4600 also includes movableelectrodes 4660 between the front substrate 4610 and the backplate 4650.

The interferometric modulator display device 4600 further includesspacers 4630 to maintain a space 4635 between the front substrate 4610and the backplate 4650. In the illustrated embodiment, the spacers 4630are interposed between the movable electrodes 4660 and the backplate4650. In one embodiment, the spacers 4630 may have a height of about 0.1μm to about 20 μm.

Referring to FIG. 46B, one of the spacers 4630 extends from thebackplate 4650 and pins a movable electrode 4660 supported on acorresponding one of the posts 4613. The spacer 4630 and the post 4613together fix the movable electrode 4660. The spacers 4630 across thedevice 4600 also maintain a consistent space 4635 between the frontsubstrate 4610 and the backplate 4650. In one embodiment, the spacers4630 may be formed on the backplate 4650 using any suitable process(e.g., photolithography and etching) before attaching the backplate 4650to the front substrate 4610. The spacers can be deposited and patternedonto the backplate 4650 or can be integrally formed with a shapedcarrier backplate. In another embodiment, the spacers 4630 may bepatterned on the movable electrodes 4660 using any suitable process. Askilled artisan will appreciate that various techniques may be used toform the spacers 4630. Additionally, the spacers 4630 and supportstructures 4613 are both illustrated as isolated pillars; however, oneor both support structures can take the form of rails or other shapes.

Referring to FIG. 47, an interferometric modulator display device 4700includes a spacer 4731 penetrating though a movable electrode 4760. Inthe illustrated embodiment, a movable electrode 4760 includes an openingor through-hole 4761 at a position over a post 4713. The spacer 4731penetrates the movable electrode 4760 through the opening 4761. Thespacer 4731 maintains a space between the front substrate (not shown)and the backplate (not shown) of the interferometric modulator displaydevice 4700. The spacer 4731 may also prevent or minimize the lateralmovement of the movable electrode 4760 without undue interference withvertical flexing for actuation. The spacer 4731 may extend from thesupport structure 4713 of the front substrate or from the backplate (notshown). In one embodiment, the spacer 4731 may be formed on the frontsubstrate using any suitable process before attaching the backplate tothe front substrate. For example, in an embodiment in which a shapedfront substrate is used, the spacer 4731 may be formed by embossing,photolithography and etching, or inscribing. In another embodiment, thespacer 4731 may be patterned on the backplate using any suitable processbefore attaching the backplate to the front substrate. In a variant ofthe above, the spacer 4731 and pattered movable electrode 4760 are bothprovided on a carrier backplate that is mounted onto the frontsubstrate. A skilled artisan will appreciate that various techniques maybe used to form the spacers 4731.

Referring to FIG. 48, an interferometric modulator display device 4800includes a front substrate 4810 and a backplate (not shown). The frontsubstrate 4810 includes rails 4811 defining troughs 4812 therebetween.The front substrate 4810 may also include posts (not shown) in thetroughs 4812. The device 4800 also includes movable electrodes 4860having at least one opening or through-hole 4861 over the rails 4811 ofthe front substrate 4810.

The interferometric modulator display device 4800 also includes a firstspacer 4832 and a second spacer 4833 on the rails 4811. The first spacer4832 penetrates the movable electrode 4860 through the opening 4861. Theconfiguration of the first spacer 4832 is similar to that of the spacer4731 of FIG. 47 except that the first spacer 4832 is positioned on therail 4811. The second spacer 4833 is positioned on the rail 4811 whilebeing laterally spaced apart from the movable electrode 4860. The secondspacer 4833 serves solely to maintain a space between the frontsubstrate and the backplate, and does not pin or fix the movableelectrode 4860. The first and second spacers 4832, 4833 may be formedusing any suitable method, for example, any of the methods for formingthe spacer 4731 of FIG. 47 described above. In addition to the rails4811, the front substrate 4810 can include posts within the troughs tostiffen the movable electrodes 4860.

Referring to FIG. 49A, an interferometric modulator display device 4900Aincludes a front substrate 4910 and a backplate 4950. The frontsubstrate 4910 includes support structures 4913 (e.g., rails or posts)defining optical cavity or gap. The device 4900A also includes movableelectrodes 4960 between the front substrate 4910 and the backplate 4960.

The interferometric modulator display device 4900A further includesspacers 4930 and stop posts 4934 a. The spacers 4930 serve to maintain adesired space 4935 between the front substrate 4910 and the backplate4950. In addition, the spacers 4930 add stiffness to the movableelectrodes 4960 by pinning them. In the illustrated embodiment, theconfiguration of the spacers 4930 may be similar to that of one of thespacers 4630, 4731 of FIGS. 46B and 47. The stop posts 4934 a arelaterally spaced apart from the support structures 4913 while extendingfrom the backplate 4950. The stop posts 4934 a do not contact themovable electrodes 4960 at the illustrated position. During theoperation of the device 4900, the stop posts 4934 a function to stop themovable electrodes 4960 when they are relaxed and move from an actuatedposition proximate to the front substrate 4910 toward the backplate4950. The stop posts 4934 a thus prevent upward overshoot of the movableelectrodes 4960. Such prevention is particularly applicable to theclosely spaced substrates 4910, 4950 of the illustrated embodiment,which facilitate hermetic sealing. With a very small volume trappedbetween the substrates 4910, 4950, it is much easier to prevent leakageinto the evacuated and hermetically sealed package. The spacers 4930 andthe stop posts 4934 a may be formed using any suitable process (e.g.,embossing, photolithography and etching, or inscribing) on the backplate4950.

Referring to FIG. 49B, an interferometric modulator display device 4900Bincludes a front substrate 4910 and a backplate 4950. The configurationsof the front substrate 4910 and the backplate 4950 can be as describedabove with reference to FIG. 49A except that stop posts 4934 b of FIG.49B contact the movable electrodes 4960 at the illustrated positionduring operation. In certain embodiments, some or all of the stop posts4934 b can adhere to the movable electrodes 4960 such that only portionsof the movable electrodes 4960 between the stop posts 4934 b collapseduring actuation. Of course, the figures are not to scale and in realitythe posts will be spaced relatively far apart. In some embodiments, thebackplate 4950 can further include rails (not shown) extendingsubstantially perpendicular to the movable electrodes 4960.

Referring to FIG. 49C, an interferometric modulator display device 4900Cincludes a front substrate 4910 and a backplate 4950. The configurationsof the front substrate 4910 and the backplate 4950 can be as describedabove with reference to FIG. 49B except that the backplate 4950 of FIG.49C does not have spacers particularly aligned with the supportstructures 4913 of the front substrate 4910. Rather, the stop posts 4934c of the backplate 4950 are distributed without regard for alignmentwith support structures 4913 of the front substrate 4910. A skilledartisan will appreciate that various other configurations of spacersand/or stop posts may also be adapted for use with the interferometricmodulator display devices 4600, 4700, 4800, 4900A-4900C.

Referring to FIG. 50, in yet another embodiment, an interferometricmodulator display device 5000 includes a front substrate 5010 having aland 5020 in the peripheral region 5002 thereof. The configuration ofthe land 5020 may be as described above with reference to FIG. 17A-17Cor 18A-18C.

The illustrated front substrate 5010 includes rails 5013, but no postsin the display region 5001 thereof. Thus, the rails 5013 and the land5020 together serve to support movable electrodes 5060 of the device5000. In addition, the land 5020 functions to define at least part of agap between the front substrate and the backplate of the device 5000.The device 5000 also includes a backplate 5050 which may include supportstructures in the form of posts 5030 from which the movable electrodes5060 are suspended. The device 5000 further includes optical stacks 5014both in the display region 5001 and in the peripheral region 5002. Thedevice 5000 also includes a sealant 5070 in the form of beads betweenthe front substrate 5010 and the backplate 5050.

Referring to FIG. 51, an interferometric modulator display device 5100includes a front substrate 5110 with no support formed thereon. Thefront substrate 5110 includes stationary electrodes 5114 formed by apatterning process, e.g., photolithography and etching. The device 5100may instead have a backplate 5170 having supports 5171 extendingtherefrom. The supports 5171 extend down to the front substrate 5110,and maintain a gap between the front substrate 5110 and the backplate5170. The device 5100 may have movable electrodes 5160 interposedbetween the front substrate 5110 and the backplate 5170. The movableelectrodes 5160 may be suspended from support structures in the form ofposts 5130 formed on the backplate 5170. Although not shown, the frontsubstrate 5110 may have a land described above to support movableelectrodes. A skilled artisan will appreciate that various othercombinations of supports are also possible.

VI. Black Mask

1. Patterned Black Mask

Referring to FIGS. 52A and 52B, an interferometric modulator displaydevice 5200 includes a front substrate 5210 and a backplate (not shown).The front substrate 5210 includes support structures in the form ofposts 5213 and cavities 5212 defined by the posts 5213. The frontsubstrate 5210 also includes an optical stack 5214 on the bottom of thecavities 5212. The device 5200 also includes a movable electrode 5262supported on the posts 5213. In FIG. 52A, the movable electrode 5260 isin its actuated position. In the actuated position, the movableelectrode 5260 is bent by electrostatic attraction toward a stationaryelectrode on the front substrate 5210. In the illustrated embodiment,one of the cavities 5212 forms a single pixel, but only part of a cavity(which may have several posts) is shown.

As shown in FIG. 52A, a central portion 5261 of the movable electrode5260 contacts or comes close to the stationary electrode in the form ofan optical stack 5214 of the front substrate 5210 while portions 5262 ofthe movable electrode 5260 proximate the support structures have a gap5212 a with the optical stack 5214. Because of the gap 5212 a, theoptical interference of light incident on non-adjoining regions Adistant from the support structures 5213 is different from that of lightincident on adjoining regions B proximate to the support structures5213. In the actuated position, the non-adjoining regions A absorb lightwhile the adjoining regions B at least partially reflect light. Such adifference in the optical interference produces a dark area in thenon-adjoining regions A and a bright area in the adjoining regions B,which tends to wash out the intended dark color.

To prevent or mitigate the bright area in the actuated position, theinterferometric modulator display device may include black masks in theadjoining regions B of the front substrate 5210. In the illustratedembodiment, the front substrate 5210 includes black masks 5220 under theoptical stack 5214 proximate to the support structures. The black masks5220 may be formed using photolithography and etching. In the context ofthis document, a black mask formed in such a manner is referred to as a“patterned” black mask. FIG. 52B illustrate a black mask 5220 viewedfrom below the front substrate 5210 as denoted by the arrow 52B in FIG.52A.

In the illustrated embodiment, an optical stack 5214 is formed on top ofthe support structures 5213. This configuration allows the device 5200not to have a black mask under the support structures 5213 because theoptical stack 5214 and the movable electrode on top act identical to anactuated movable electrode and an optical stack below, thus serving as ablack mask. The patterned black mask may apply to any of theinterferometric modulator display device embodiments described above.

2. Partial Wetting Black Mask

FIGS. 53A-53C illustrates another embodiment of a method of forming ablack mask in an interferometric modulator display device 5300. First, afront substrate 5310 is provided including support structures 5313 andcavities 5312 defined by the support structures 5313. Then, the cavities5312 are substantially filled with a black mask material 5320 a usingany suitable process, for example, spin coating or spray coating. Inanother embodiment, the front substrate 5310 may be immersed in a blackmask material suspension or solution in a container. The black maskmaterial 5320 a may include a black pigment and an organic solvent. Theblack mask material 5320 a may have a density or viscosity adapted forthe processes described below. In one embodiment, the black pigment maybe an organic material. In another embodiment, the black pigment may bean inorganic material. Examples of the black pigment include, but arenot limited to, copper oxide, graphite, and carbon black. Examples ofthe solvent include, but are not limited to, acetone and isopropylalcohol (IPA). In some embodiments, the black mask material may alsoinclude a photoresist and/or a polymeric material (e.g., thermosettingpolymer).

Next, the solvent is removed from the cavities 5312 while leaving theblack pigment in the cavities 5312. In one embodiment, the solvent maybe removed by drying. In certain embodiments, the front substrate 5310may be heated to facilitate drying of the solvent. Then, the surfacetension of the black mask material 5320 a drives a substantial portionof the material 5320 a to regions proximate to the support structures5313 while the solvent is being removed. Thus, a substantial portion ofthe black pigment remains near the support structures 5313 (e.g., withinabout 1 μm to about 10 μm from the posts 5313), thereby forming blackmasks 5320 b, as shown in FIG. 53B. Subsequently, an optical stack 5214is formed over the front substrate 5310, as shown in FIG. 53C. Inanother embodiment, a black mask 5320 b may be formed after an opticalstack 5314 is formed on a shaped front substrate 5310, as shown in FIG.53D in a manner similar to that shown in FIGS. 53A and 53B. A black maskformed in the manner shown in FIGS. 53A-53D may be referred to as apartial wetting black mask in the context of this document. The partialwetting black mask may apply to the embodiments in which a shaped frontsubstrate or a preformed support substrate is used. A skilled artisanwill appreciate that the partial wetting black mask may be adapted foruse in the various embodiments described above. In the illustratedembodiment, an optical stack 5314 on top of the support structures 5313and a movable electrode (not shown) overlying the optical stack 5314together serve as a black mask similar to those shown in FIG. 52A.

VII. Static Interferometric Display

It will be understood that although the embodiments of interferometricmodulators discussed above relate to interferometric modulators havingmovable electrodes, other embodiments are possible. In particular, astatic interferometric display may be provided, which includes a firstpartially reflective layer and a second layer which is at leastpartially reflective, separated by an interferometric gap defined by airor a light-transmissive material. The term “static interferometricdisplay” refers to a device configured to display a static image usinginterferometric effect. The static image can include a black and whiteimage and/or a color image, and may include patterns on a singleinterferometric gap.

It will be understood that the second reflective layer may be partiallyreflective, or may be fully reflective, depending on the embodiment. Forconvenience, the first partially reflective layer, for which partialtransmission is functionally significant, may be referred to herein as apartially reflective layer, and the second reflective layer may bereferred to as a reflective layer, and the two layers together may bereferred to collectively as reflective layers, although it will beunderstood that the use of the term reflective layer is not intended toexclude partially reflective layers. Similarly, the partially reflectivelayer may be alternately referred to as an absorber.

In such a static interferometric display, there is no need to select orinclude conductive materials for use as electrodes, as the staticinterferometric display is not intended to be electrostaticallyactuatable. Similarly, the reflective layers need not be electricallyisolated from one another, as there is no need to apply a voltage acrossthe two layers (because there is neither movement nor relaxation from anactuated state). Thus, non-conductive material may be used to form thereflective layers, and conductive material may be used to define theinterferometric gap. A static interferometric display may comprise anair gap instead of a light-transmissive layer. In further embodiments, astatic interferometric display may be identical to an actuatableinterferometric modulator, and may simply not be actuated. It will beunderstood that the use of a solid material to define the air gap mayprovide additional stability, however, in addition to further possibleadvantages discussed below.

In some embodiments, a static interferometric display can be formed byattaching two substrates, each of which has components preformedthereon, similar to the MEMS devices described above with reference toFIG. 9. In such embodiments, no sacrificial material is needed forpreforming the components (e.g., cavities) on the substrates, as withpreviously described embodiments. In attaching the two substrates, anysuitable technique (e.g., lamination, bonding, etc.) can be used.

In one embodiment, a static interferometric display may be formed byattaching a front substrate to a backplate. The “front substrate,” asemployed herein, is generally transparent and faces the viewer. At leastone of the front substrate and the backplate may be shaped to formcavities of selected depth for interferometric modulation. The cavitiesmay be formed by any suitable process, e.g., embossing, photolithographyand etching, and inscribing.

1. Static Interferometric Display with Shaped or Preformed Support FrontSubstrate

FIG. 54 illustrates the pre-lamination state of a static interferometricdisplay 5400 according to one embodiment. The static interferometricdisplay 5400 includes a front substrate 5410 and a backplate 5420. Thefront substrate 5410 includes a plurality of rails 5411 and a pluralityof cavities or recesses 5430 defined by the rails 5411. In the contextof this document, the rails 5411 may also be referred to as “supports”or “support structures.” The front substrate 5410 also includes anoptical layer or optical stack 5414 a on top of the rails 5411 and thesame optical layer or stack 5414 b on the bottom of the cavities 5430.As described above with reference to FIG. 11A, the optical layer orstack 5414 a on top of the rails 5411 can provide black or white color,depending on the interferometric display design, as governed by theoptical thickness of the optical layer or stack 5414 a. The backplate5420 includes a reflective layer (or mirror) 5421 facing the frontsubstrate 5410.

The front substrate 5410 may be formed of a substantially transparentmaterial. Examples of the transparent material include, but are notlimited to, glass and transparent polymeric materials. The frontsubstrate 5410 may be shaped by any method suitable for removing orshaping portions of the front substrate 5410 or forming recesses into asurface of the substrate 5410. Examples of shaping methods include, butare not limited to, embossing (e.g., the method described with referenceto FIGS. 12A-12C), photolithography (or screen printing) and etching,and inscribing. Because the substrate 5410 may be shaped without addingan additional material to the substrate 5410 in at least some of themethods described above, the supports in the form of the rails 5411 maybe formed integrally with and of the same material as that of the frontsubstrate 5410. In other embodiments, support structures can be formedon a substantially planar front substrate by deposition and patterningof an additional material, as described above with respect to thepreformed support front substrate.

Each of the rails 5411 extends in either a row direction or a columndirection parallel to one another, as shown in FIG. 56. The illustratedrails 5411 define cavities of a square shape arranged in a grid ormatrix form. In other embodiments, the cavities can have various othershapes when viewed from above, e.g., rectangle, triangle, circle, oval,etc., and the grid need not be orthogonal. Indeed, the image can haveany desired pattern, since there are no issues with respect toelectrically addressing pixels. The rails 5411 have their top surfacesat substantially the same level, i.e., within a single plane.

The cavities 5430 are defined to have multiple depths 5450 a-5450 e,depending on the colors which the cavities 5430 are designed to producein the resulting display. For optimal clarity and sharpness of color,the depths 5450 a-5450 e may be in a range from about 500 Å to about5,000 Å. While interferometric effects can also be obtained with greateroptical depth, the skilled artisan will appreciate that colors begin towash out with greater depth as the optical distances correspond tomultiples of a variety of wavelengths. In other embodiments in whichfillers are used (e.g., FIGS. 57, 58, 60, and 61), the depths of thecavities given for air may be adjusted for such fillers because thefillers can have different optical density (index of refraction).Because the static interferometric display 5400 only displays a staticimage, the depths of the cavities are selected according to the patternof the desired static image. A skilled artisan will appreciate suitabledepths 5450 a-5450 e for producing desired colors and patterns usinginterferometric effect.

The optical stacks 5414 a, 5414 b may be a single layer or may includeseveral fused layers. In one embodiment, the optical stacks 5414 a, 5414b may be formed of a dielectric material having an absorptioncoefficient suitable for interferometric effect. Examples of thedielectric material include, but are not limited to, silicon dioxide andaluminum oxide. In another embodiment, the optical stack 5414 a, 5414 bmay have a two-layered structure, including an upper sublayer and alower sublayer. The upper sublayer may be formed of aluminum oxide. Thelower sublayer may be formed of silicon dioxide.

In one embodiment, the optical stacks 5414 a, 5414 b may have athickness between about 100 Å and about 1,600 Å. In the embodiment inwhich the optical stacks 5414 a, 5414 b have upper and lower sublayers,the upper sublayer may have a thickness of, for example, about 50 Å,while the lower sublayer may have a thickness of, for example, about 450Å. In the illustrated embodiment, the optical stacks 5414 a, 5414 b arediscontinuous between the bottom of the cavities 5430 and the top of therails 5411 due to a directional deposition, such as sputtering.

In certain embodiments, the optical stacks 5414 a, 5414 b may alsoinclude a metallic absorber layer (or a partially reflective layer). Theabsorber layer may be formed of a semi-transparent thickness of metal,such as chromium (Cr) or germanium (Ge). The absorber layer may have athickness between about 1 Å and about 100 Å, particularly between about50 Å and about 100 Å.

In certain embodiments, the front substrate 5410 itself may be formed ofa material having optical dispersion (index of refraction and absorptioncoefficient) suitable for interferometric effect. In such embodiments,the front substrate 5410 may not include optical stacks.

The backplate 5420 may be formed of any suitable material (e.g., apolymer, metal, and glass). The reflective layer 5421 of the backplate5420 may be formed of a specular or reflective metal, for example, Al,Au, Ag, or an alloy of the foregoing, and is preferably thick enough toreflect substantially all visible light incident upon the frontsubstrate 5410 for interferometric effect. In an exemplary embodiment,the reflective layer 5421 has a thickness of about 300 Å. Thethicknesses of the reflective layer 5421 may vary widely in otherembodiments. In certain embodiments, the backplate 5420 itself may beformed of a reflective material such as an aluminum foil. In suchembodiments, the backplate 5420 does not include a separate reflectivelayer.

In the illustrated embodiment, the backplate 5420 is mounted on thefront substrate 5410 as denoted by arrows such that the reflective layer5421 contacts the top surfaces of the optical stacks 5414 a on the rails5411. The resulting static interferometric display 5400 may havesubstantially no gap between the reflective layer 5421 and the topsurfaces of the optical stacks 5414 a on the rails 5411.

2. Static Interferometric Display with Shaped or Preformed Backplate

FIG. 55 illustrates the pre-lamination state of a static interferometricdisplay 5500 according to another embodiment. The static interferometricdisplay 5500 includes a front substrate 5510 and a backplate 5520. Thefront substrate 5510 includes a substantially planar surface 5511, andan optical layer or stack 5514 formed on the surface 5511. The backplate5520 includes a plurality of rails 5523 and a plurality of cavities orrecesses 5530 defined by the rails 5523. In the context of thisdocument, the rails 5523 may also be referred to as “supports” or“support structures.” The backplate 5520 also includes a reflectivelayer (or mirror) 5521 facing the front substrate 5510.

The configuration of the front substrate 5510 can be as described abovewith respect to that of the front substrate 5410 of FIG. 54 except thatthe front substrate 5510 of FIG. 55 is substantially planar. Theconfiguration of the optical layers or stack 5514 can be as describedabove with respect to that of the optical layers or stacks 5414 a, 5414b of FIG. 54 except that the optical layer or stack 5514 of FIG. 55 issubstantially continuously formed on the surface of the front substrate5510. In certain embodiments, the front substrate 5510 itself may beformed of a material having an absorption coefficient suitable forinterferometric effect. In such embodiments, the front substrate 5510may omit an optical stack.

The backplate 5520 may be formed of a material suitable for shaping.Examples of the material include, but are not limited to, glass, metal,and polymer. The backplate 5520 may be shaped by any method suitable forremoving or shaping portions of the front substrate 5520 or formingrecesses into a surface of the backplate 5520. Examples of shapingmethods include, but are not limited to, embossing (e.g., the methoddescribed with reference to FIGS. 12A-12C), photolithography (or screenprinting) and etching, and inscribing. Because the backplate 5520 isshaped without adding an additional material to the backplate 5520 inthe methods described above, the supports in the form of the rails 5523may be formed integrally with and of the same material as that of thebackplate 5520. In other embodiments, support structures can be formedon a substantially planar backplate by deposition and patterning of anadditional material, as described above with respect to the preformedsupport front substrate.

The rails 5523 extend in either a row direction or a column directionparallel to one another, similar to the pattern shown in FIG. 56. Therails 5523 have their bottom surfaces (facing the front substrate) atsubstantially the same level, i.e., within a single plane.

The cavities 5530 are shaped or preformed to have multiple depths 5550a-5550 e, depending on the colors which the cavities 5530 are designedto produce in the resulting display. Because the static interferometricdisplay 5500 only displays a static image, the depths of the cavitiesare selected according to the pattern of the desired static image. Askilled artisan will appreciate suitable depths 5550 a-5550 e forproducing desired colors and patterns using interferometric effect.

The reflective layer 5521 of the backplate 5520 may be formed of aspecular or reflective metal, for example, Al, Au, Ag, or an alloy ofthe foregoing, and is thick enough to reflect substantially all visiblelight incident upon the front substrate 5510 for interferometric effect.In an exemplary embodiment, the reflective layer 5521 has a thickness ofabout 300 Å. The thicknesses of the reflective layer 5521 may varywidely in other embodiments. In certain embodiments, a backplate may beformed of a reflective material such as aluminum. Such a backplate maybe etched to form support structures. In such embodiments, the backplatemay not include a separate reflective layer. In the illustratedembodiment, the reflective layer 5521 is continuously formed on surfacesof the backplate 5520. In other embodiments, the reflective layer 5521may be discontinuous between the rails 5523 and the cavities 5530.

In the illustrated embodiment, the backplate 5520 is mounted on thefront substrate 5510 as denoted by arrows such that the lowermostsurfaces of the reflective layer 5521 (the bottom surfaces of thereflective layer 5521 underlying the rails 5523 and facing the frontsubstrate 5510) contact the top surface of the optical stack 5514 of thefront substrate 5510. The resulting static interferometric display 5500may have substantially no gap between the lowermost surfaces of thereflective layer 5521 and the top surface of the optical stack 5514 ofthe front substrate 5510.

3. Static Interferometric Display with Cavity Filler

FIG. 57 illustrates the pre-lamination state of a static interferometricdisplay 5700 according to another embodiment. The static interferometricdisplay 5700 includes a front substrate 5710 and a backplate 5720. Theconfiguration of the front substrate 5710 can be as described above withrespect to that of the front substrate 5410 of FIG. 54. Theconfiguration of the backplate 5720 can be as described above withrespect to that of the backplate 5420 of FIG. 54. The top plan view ofthe static interferometric display 5700 can be as described above withreference to FIG. 56.

The static interferometric display 5700 further includes a filler 5760within the cavities of the front substrate 5710. The filler 5760 may beformed of a substantially transparent material. The substantiallytransparent material may have a suitable refractive index forinterferometric effect. Examples of the substantially transparentmaterial include, but are not limited to, oxides (e.g., SiO₂, TiO₂),nitrides (e.g., SiN₃, SiN₄), transparent photoresists, and transparentpolymers. The filler 5760 may be formed by blanket depositing a fillermaterial on the front substrate 5700 with the optical stacks 5714 a,5714 b formed thereon, and then planarizing the top surface of thefiller material. In certain embodiments, the filler may also cover thetop surfaces of the optical stacks 5714 a on the rails 5711.

In the illustrated embodiment, the backplate 5720 is mounted on thefront substrate 5710 as denoted by arrows such that the lowermostsurface of the reflective layer 5721 (facing the front substrate)contacts the top surface of the filler 5760 formed on the frontsubstrate 5710. The resulting static interferometric display 5700 mayhave substantially no gap between the lowermost surface of thereflective layer 5721 and the top surface of the filler 5760. In certainembodiments, a reflective layer may be coated directly on the filler5760. Then, a top surface of the reflective layer may be coated with amaterial having hardness suitable for protecting the reflective layer,instead of laminating a separate backplate. In other embodiments, abackplate may be attached to the reflective layer which has beendirectly formed on the filler 5760.

FIG. 58 illustrates a static interferometric display 5800 according toanother embodiment. The static interferometric display 5800 includes afront substrate 5810 and a backplate 5820. The configuration of thefront substrate 5810 can be as described above with respect to that ofthe front substrate 5710 of FIG. 57 except that the front substrate 5810of FIG. 58 does not include rails. The front substrate 5810 includescavities having discrete depths which form a stepped surface. Theillustrated front substrate 5810 includes a filler 5860 similar to thefiller 5760 of FIG. 5760. The filler 5860 may be formed by blanketdepositing a filler material on the front substrate 5800 with theoptical stacks 5814 formed thereon, and then planarizing the top surfaceof the filler material. The configuration of the backplate 5820 can beas described above with respect to that of the backplate 5720 of FIG.57.

FIG. 59 illustrates a top plan view of a portion of the staticinterferometric display 5800 of FIG. 58. Because the staticinterferometric display 5800 includes no rails, it does not havepartitions when viewed from above, as shown in FIG. 59. The staticinterferometric display 5800 includes square-shaped pixels P1-P15. Askilled artisan will appreciate that a static interferometric displaycan have various other shapes of pixels and that the grid need not beorthogonal. Indeed, the image can have any desired pattern, since pixelsneed not be electrically addressed.

FIG. 60 illustrates a static interferometric display 6000 according toanother embodiment. The static interferometric display 6000 includes afront substrate 6010 and a backplate 6020. The configuration of thefront substrate 6010 can be as described above with respect to that ofthe front substrate 5510 of FIG. 55. The configuration of the backplate6020 can be as described above with respect to that of the backplate5520 of FIG. 55 except that the backplate 6020 of FIG. 60 does notinclude rails.

The illustrated backplate 6020 includes a filler 6060 similar to thefiller 5860 of FIG. 58. The filler 6060 may be formed by blanketdepositing a filler material on the backplate 6020 with a reflectivelayer 6021 formed thereon, and then planarizing the top surface of thefiller material. Then, the backplate 6020 with the filler 6060 may beattached to the front substrate 6010 with an optical stack 6014 formedthereon, thereby forming a static interferometric display. The top planview of the static interferometric display 6000 can be as describedabove with reference to FIG. 59.

4. Static Interferometric Display with Continuous Depth Cavities

FIG. 61 illustrates a static interferometric display 6100 according toanother embodiment. The static interferometric display 6100 includes afront substrate 6110 and a backplate 6120. The configuration of thefront substrate 6110 can be as described above with respect to that ofthe front substrate 5810 of FIG. 58 except that the front substrate 6110of FIG. 61 includes cavities having depths which are continuous orsmoothly transitioning rather than discrete. The front substrate 6110also includes a filler 6160 similar to the filler 5860 of FIG. 58. Theconfiguration of the backplate 6120 can be as described above withrespect to that of the backplate 5820 of FIG. 58. In another embodiment,the backplate may have cavities having continuous or smoothlytransitioning depths while the front substrate is substantially flat. Askilled artisan will appreciate that various other combinations of frontsubstrates and backplates are also possible.

In some of the embodiments described above, a front substrate and/orcarrier (either permanent or removable) are shaped and discontinuousdeposition is performed thereon. This method avoids expensive maskingsteps, thus reducing manufacturing costs. In addition, spacers,supports, stop posts formed on a back carrier each lead to betteruniformity and reliability, and less pressure variation and moisturesusceptibility with a smaller gap.

The embodiments, although described with respect to an interferometricmodulator display device, are applicable more generally to other MEMSdevices, particularly electrostatic MEMS with electrodes capable ofrelative movement.

While the above detailed description has shown, described, and pointedout novel features of the invention as applied to various embodiments,it will be understood that various omissions, substitutions, and changesin the form and details of the device or process illustrated may be madeby those skilled in the art without departing from the spirit of theinvention. As will be recognized, the present invention may be embodiedwithin a form that does not provide all of the features and benefits setforth herein, as some features may be used or practiced separately fromothers.

The invention claimed is:
 1. An electromechanical system device,comprising: a front substrate having a first surface, the frontsubstrate including an optical stack formed over the first surface; abackplate opposing the front substrate, the backplate having a secondsurface facing the first surface, the backplate including: supportsextending from the second surface toward the first surface such that theheight of the supports defines a distance between the first surface andthe second surface; and a plurality of posts projecting from thebackplate towards the front substrate; and a plurality of movableelectrode strips extending substantially parallel to one another, thestrips being suspended from the plurality of posts, spaced apart fromthe front substrate and the backplate, and interposed between the firstsurface and the second surface.
 2. The device of claim 1, wherein thefirst surface of the front substrate includes an array region withinwhich the movable electrode strips are positioned, and wherein the arrayregion of the first surface is devoid of posts.
 3. The device of claim1, wherein the optical stack over the first surface is discontinuous. 4.The device of claim 1, wherein the optical stack includes a partiallyreflective layer.
 5. The device of claim 4, wherein the optical stackfurther includes an electrode layer.
 6. The device of claim 4, whereinthe optical stack and at least one of the movable electrode stripsconstitute an interferometric modulator.
 7. The device of claim 1,wherein the front substrate includes a peripheral region including aland, wherein the land supports portions of the movable electrodestrips.
 8. The device of claim 1, wherein the front substrate includes aplurality of stationary electrodes separated by a gap from the movableelectrode strips.
 9. An electromechanical system device, comprising: afront substrate; a backplate opposing the front substrate, the backplatehaving a surface facing the front substrate; a plurality of movableelectrode strips extending substantially parallel to one another, thestrips being interposed between the front substrate and the backplate,portions of the strips being movable toward the front substrate; and aplurality of spacers extending from the surface of the backplate suchthat the spacers are arranged to limit movement of the portions of thestrips toward the surface of the backplate.
 10. The device of claim 9,wherein the plurality of movable electrode strips are suspended from theplurality of spacers.
 11. The device of claim 9, further comprising aplurality of first supports extending from the front substrate towardthe backplate, each of the first supports including at least one of apost and a rail.
 12. The device of claim 11, wherein portions of themovable electrode strips are interposed between the first supports andthe spacers of the backplate.
 13. The device of claim 11, wherein thefront substrate includes an optical stack between the front substrateand the backplate.
 14. The device of claim 13, wherein theelectromechanical system device includes an interferometric modulatorincluding a reflective layer and at least one of the movable electrodestrips.
 15. The device of claim 13, wherein portions of the opticalstack are between the first supports and the movable electrode strips.16. The device of claim 11, wherein the movable electrode strips includeopenings and wherein the spacers extend through the openings.
 17. Thedevice of claim 9, wherein the backplate includes a plurality of stopposts configured to prevent overshoot of the movable electrode stripstowards the backplate.
 18. The device of claim 17, wherein the movableelectrode strips are suspended from the stop posts.
 19. The device ofclaim 17, wherein the movable electrode strips do not contact the stopposts.
 20. An electromechanical system device, comprising: a frontsubstrate having a first surface, the front substrate including anoptical stack formed over the first surface; a backplate opposing thefront substrate, the backplate having a second surface facing the firstsurface, the backplate including supports extending from the secondsurface toward the first surface such that the height of the supportsdefines a distance between the first surface and the second surface; anda plurality of movable electrode strips extending substantially parallelto one another, the strips being interposed between the first surfaceand the second surface, wherein the optical stack includes a partiallyreflective layer.
 21. The device of claim 20, wherein the first surfaceof the front substrate includes an array region within which the movableelectrode strips are positioned, and wherein the array region of thefirst surface is devoid of posts.
 22. The device of claim 20, whereinthe optical stack over the first surface is discontinuous.
 23. Thedevice of claim 20, wherein the optical stack further includes anelectrode layer.
 24. The device of claim 20, wherein the optical stackand at least one of the movable electrode strips constitute aninterferometric modulator.
 25. The device of claim 20, wherein the frontsubstrate includes a peripheral region including a land, wherein theland supports portions of the movable electrode strips.
 26. The deviceof claim 20, wherein the front substrate includes a plurality ofstationary electrodes separated by a gap from the movable electrodestrips.